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  • 1.
    Abbas, Alaa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Palladium-Catalysed Carbonylative Synthesis of Acylamidines2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 2. Abbasi, Alireza
    et al.
    Skripkin, Mikhail Yu.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Torapava, Natallia
    Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 5, 1111-1118 p.Article in journal (Refereed)
    Abstract [en]

    The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-kappa O)(5)(dmso-kappa S)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-kappa O)(3)(dmso-kappa S)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) angstrom (1) and 2.100(6) angstrom (1*), than the mean Rh-O bond distance with O trans to O, 2.019 angstrom (1) and 2.043 angstrom (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 angstrom, is slightly longer than that for O trans to Cl, 2.067(4) angstrom, which is consistent with the trans influence DMSO-kappa S > Cl > DMSO-kappa O of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.

  • 3. Abdel-Hamid, Mohammed K
    et al.
    Macgregor, Kylie A
    Odell, Luke R
    Chau, Ngoc
    Mariana, Anna
    Whiting, Ainslie
    Robinson, Phillip J
    McCluskey, Adam
    1,8-Naphthalimide derivatives: new leads against dynamin I GTPase activity.2015In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, no 29Article in journal (Refereed)
    Abstract [en]

    Fragment-based in silico screening against dynamin I (dynI) GTPase activity identified the 1,8-naphthalimide framework as a potential scaffold for the design of new inhibitors targeting the GTP binding pocket of dynI. Structure-based design, synthesis and subsequent optimization resulted in the development of a library of 1,8-naphthalimide derivatives, called the Naphthaladyn™ series, with compounds 23 and 29 being the most active (IC50 of 19.1 ± 0.3 and 18.5 ± 1.7 μM respectively). Compound 29 showed effective inhibition of clathrin-mediated endocytosis (IC50(CME) 66 μM). The results introduce 29 as an optimised GTP-competitive lead Naphthaladyn™ compound for the further development of naphthalimide-based dynI GTPase inhibitors.

  • 4.
    Acharya, P
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Bioorganic Chemistry.
    Chattopadhyaya, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Bioorganic Chemistry.
    The Hydrogen Bonding and Hydration of 2'-OH in Adenosine and Adenosine 3'-ethylphosphate.2002In: J. Org. Chem., Vol. 67, 1852-1865 p.Article in journal (Refereed)
  • 5.
    Acharya, Parag
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Bioorganic Chemistry.
    Studies on the Non-covalent Interactions (Stereoelectronics, Stacking and Hydrogen Bonding) in the Self-assembly of DNA and RNA2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on ten publications (Papers I-X). The phosphodiester backbone makes DNA or RNA to behave as polyelectrolyte, the pentose sugar gives the flexibility, and the aglycones promote the self-assembly or the ligand-binding process. The hydrogen bonding, stacking, stereoelectronics and hydration are few of the important non-covalent forces dictating the self-assembly of DNA/RNA. The pH-dependent thermodynamics clearly show (Papers I and II) that a change of the electronic character of aglycone modulates the conformation of the sugar moiety by the tunable interplay of stereoelectronic anomeric and gauche effects, which are further transmitted to steer the sugar-phosphate backbone conformation in a cooperative manner. 3'-anthraniloyl adenosine (a mimic of 3'-teminal CCAOH of the aminoacyl-tRNAPhe) binds to EF-Tu*GTP in preference over 2'-anthraniloyl adenosine, thereby showing (Paper III) that the 2’-endo sugar conformation is a more suitable mimic of the transition state geometry than the 3’-endo conformation in discriminating between correctly and incorrectly charged aminoacyl-tRNAPhe by EF-Tu during protein synthesis. The presence of 2'-OH in RNA distinguishes it from DNA both functionally as well as structurally. This work (Paper IV) provides straightforward NMR evidence to show that the 2'-OH is intramolecularly hydrogen bonded with the vicinal 3'-oxygen, and the exposure of the 3'-phosphate of the ribonucleotides to the bulk water determines the availability of the bound water around the vicinal 2'-OH, which then can play various functional role through inter- or intramolecular interactions. The pH-dependent 1H NMR study with nicotinamide derivatives demonstrates (Paper V) that the cascade of intramolecular cation (pyridinium)-π(phenyl)-CH(methyl) interaction in edge-to-face geometry is responsible for perturbing the pKa of the pyridine-nitrogen as well as for the modulation of the aromatic character of the neighboring phenyl moiety, which is also supported by the T1 relaxation studies and ab initio calculations. It has been found (Papers VI-IX) that the variable intramolecular electrostatic interaction between electronically coupled nearest neighbor nucleobases (steered by their respective microenvironments) can modulate their respective pseudoaromatic characters. The net result of this pseudoaromatic cross-modulation is the creation of a unique set of aglycones in an oligo or polynucleotide, whose physico-chemical properties are completely dependent upon the propensity and geometry of the nearest neighbor interactions (extended genetic code). The propagation of the interplay of these electrostatic interactions across the hexameric ssDNA chain is considerably less favoured (effectively up to the fourth nucleobase) compared to that of the isosequential ssRNA (up to the sixth nucleobase). The dissection of the relative strength of basepairing and stacking in a duplex shows that stability of DNA-DNA duplex weakens over the corresponding RNA-RNA duplexes with the increasing content of A-T/U base pairs, while the strength of stacking of A-T rich DNA-DNA duplex increases in comparison with A-U rich sequence in RNA-RNA duplexes (Paper X).

  • 6.
    Adbo, Karina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Andersson, Håkan S.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Ankarloo, Jonas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Karlsson, Jesper G.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Norell, M C
    Olofsson, Linus
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Svenson, Johan
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Örtegren, U
    Nicholls, Ian A.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Enantioselective synthetic receptors for Tröger’s base1999In: Bioorganic Chemistry, Vol. 27, no 5, 363-371 p.Article in journal (Refereed)
  • 7.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalyzed epoxidation of alkenes2010In: Modern Oxidation Methods / [ed] Jan-Erling Bäckvall, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 2, 37-84 p.Chapter in book (Other academic)
  • 8.
    Adrian Meredith, Jenny
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design and Synthesis of Inhibitors Targeting the Aspartic Proteases HIV-1 PR and BACE-12009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the synthesis of molecules designed for inhibition of two aspartic proteases, viral HIV-1 PR and human BACE-1. It also reports on the structure activity relationships of the targeted enzyme inhibitors.

    It is estimated that currently 33 million people are infected with HIV, the causative agent of AIDS. The virus targets T-lymphocytes and macrophages of the human immune system. The HIV-1 PR plays an important role in the viral replication, and by inhibiting the enzyme the disease progression can be slowed down or even halted.

    Herein is reported the design and synthesis of a series of HIV-1 PR inhibitors with novel P2 substituents of which several inhibit the enzyme in the nanomolar range. The aim of the second work was to further develop the inhibitors by the introduction of fluorine. Several attempts were performed to fluorinate different P2-substituents.

    Alzheimer’s disease (AD) is neurodegenerative, progressive and fatal disorder of the brain. It is associated with accumulation of plaques and tangles that cause impairment and functional decline of brain tissue which result in loss of memory and cognition. The plaques are mainly constituted of amyloid-β peptides that are generated in two steps from the amyloid precursor protein (APP). The cleavage sequence is initiated by the aspartic protease BACE-1, which makes the enzyme a key target in the effort of finding a therapy that aim to slow down the progression of AD.

    Herein are enclosed the development of two series of potent BACE-1 inhibitors. In the first work a synthetic strategy was developed to truncate a previously reported hydroxyethylene core structure in order to generate more drug-like inhibitors. This generated a series of truncated inhibitors where two amide bonds have been replaced with an ether - or alternatively a secondary amine linkage. A number of these inhibitors show potency against BACE-1. In the second part of the work the aim was investigate the effect of alterations in the P1 position. Five scaffolds with new P1 substituents were designed, synthesized and coupled with two different P2-P3 substituents. This resulted in a series of potent inhibitors that inhibit BACE-1 in the nanomolar range.

  • 9. Aeluri, Madhu
    et al.
    Pramanik, Chinmoy
    Chetia, Lakshindra
    Mallurwar, Naveen Kumar
    Balasubramanian, Sridhar
    Chandrasekar, Gayathri
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
    Kitambi, Satish Srinivas
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies. Karolinska Institute.
    Arya, Prabhat
    14-Membered Macrocyclic Ring-Derived Toolbox: The Identification of Small Molecule Inhibitors of Angiogenesis and Early Embryo Development in Zebrafish Assay2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 3, 436-439 p.Article in journal (Other academic)
    Abstract [en]

    A highly practical and modular synthesis to obtain a diverse 14-membered ring-based macrocyclic toolbox is achieved. These compounds were further tested in zebrafish assays related to early embryonic development, angiogenesis, and neurogenesis, respectively. 1.4c was Identified as an antiangiogenesis agent.

  • 10.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Direct regiospecific and highly enantioselective intermolecular a-allylic alkylation of aldehydes by combination of transition metal and chiral amine catalysts2012Conference paper (Refereed)
    Abstract [en]

    The direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by combination of achiral bench stable Pd(0) complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 er). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals and 2-alkyl-butane-1,4-diols.

  • 11. Afewerki, Samson
    et al.
    Breistein, Palle
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective β -alkylation of α,β-unsaturated aldehydes by combination of transition-metal- and aminocatalysis: Total synthesis of bisabolane sesquiterpenes2011In: Chemistry: a European Journal, ISSN 0947-6539, Vol. 17, no 32, 8784-8788 p.Article in journal (Refereed)
  • 12.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Breistein, Palle
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Pirttilä, Kristian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Deiana, Luca
    Univ Stockholm, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden.
    Dziedzic, Pawel
    Univ Stockholm, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Catalytic Enantioselective beta-Alkylation of alpha,beta-Unsaturated Aldehydes by Combination of Transition-Metal- and Aminocatalysis: Total Synthesis of Bisabolane Sesquiterpenes2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 32, 8784-8788 p.Article in journal (Refereed)
    Abstract [en]

    Branching out! The first co-catalytic enantioselective (up to 98:2 e.r.) β-alkylation of α,β-unsaturated aldehydes by combination of simple chiral amine and copper catalysts provides β-branched aldehydes in a one-pot protocol (see scheme). The methodology was applied to the short total syntheses of bisabolane sesquiterpenes (S)-(+)-curcumene, (E)-(S)-(+)-3- dehydrocurcumene and (S)-(+)-tumerone. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 13. Afewerki, Samson
    et al.
    Ibrahem, Ismail
    Rydfjord, Jonas
    Breistein, Palle
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct Regiospecific and Highly Enantioselective Intermolecular α-Allylic Alkylation of Aldehydes by a Combination of Transition-Metal and Chiral Amine Catalysts2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 10, 2972-2977 p.Article in journal (Refereed)
    Abstract [en]

    The first direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.

  • 14.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Rydfjord, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Breistein, Palle
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Direct Regiospecific and Highly Enantioselective Intermolecular α-Allylic Alkylation of Aldehydes By Combination of Transition Metal and amine Catalysts2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 10, 2972-2977 p.Article in journal (Refereed)
    Abstract [en]

    The first direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd 0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecificα-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed. Go organic! Directintermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd 0complexes and simple chiral amines as co-catalysts is disclosed (see scheme). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 15. Agasti, Soumitra
    et al.
    Maity, Soham
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Maiti, Debabrata
    Palladium-Catalyzed Synthesis of 2,3-Disubstituted Benzofurans: An Approach Towards the Synthesis of Deuterium Labeled Compounds2015In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 357, no 10, 2331-2338 p.Article in journal (Refereed)
    Abstract [en]

    Palladium-catalyzed oxidative annulations between phenols and alkenylcarboxylic acids produced a library of benzofuran compounds. Depending on the nature of the substitution of the phenol precursor, either 2,3-dialkylbenzofurans or 2-alkyl-3-methylene-2,3-dihydrobenzofurans can be synthesized with excellent regioselectivity. Reactions between conjugated 5-phenylpenta-2,4-dienoic acids and phenol gave 3-alkylidenedihydrobenzofuran alkaloid motifs while biologically active 7-arylbenzofuran derivatives were prepared by starting from 2-phenylphenols. More interestingly, selective incorporation of deuterium from D2O has been discovered, which offers an attractive one-step method to access deuterated compounds.

  • 16.
    Aggarwal, Varinder K.
    et al.
    Bristol University.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of Bristol, Bristol, UK.
    Enantioselective α-arylation of cyclohexanones with diaryl iodonium salts: Application to the synthesis of (-)-epibatidine.2005In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 44, no 34, 5516-5519 p.Article in journal (Refereed)
    Abstract [en]

    The direct asym. α-arylation of prochiral ketones has been effected using chiral lithium amide bases and diaryl iodonium salts. The methodol. has been employed in a short total synthesis of the alkaloid (-)-epibatidine. [on SciFinder(R)]

  • 17.
    Agnemo, Roland
    Umeå University, Faculty of Science and Technology.
    Ligniners reaktioner med alkalisk väteperoxid1981Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Under alkaline conditions hydrogen peroxide can be used either as a 1ignin-degrading or a 1ignin-preserving bleaching agent. If heavy metal ions are present and/or silicate is absent in the reaction medium, hydrogen peroxide decomposes via hydroxyl radicals and superoxide ions to oxygen and water. These decomposition products are able to react for example with phenolic lignin structures and thereby cause a partial degradation of lignin. In such a system peroxide could act as a bleaching and delignifying agent at the same time and these properties can be utilized for the bleaching of chemical pulps.In order to elucidate the factors which influence the degradation of phenolic structures by oxidation with alkaline hydrogen peroxide the lignin model compounds-methylsyringyl alcohol was studied.By determining the first order reaction rate constants for the oxidation, the main results which were obtained indicate that phenolic lignin structures can be efficiently degraded especially if:A. The pH in the bleaching liquor is close to the pK -valueàfor hydrogen peroxide.B. The ionic strength in the bleaching medium is as high as possible.C. A fixed amount of heavy metal ions (manganese) is added to the bleaching liquor.In the presence of silicate and diethylentriaminepenta-acetic acid (DTPA) hydrogen peroxide is stabilized against decomposition. Under these conditions alkaline hydrogen peroxide is able to react only with lignin units containing conjugated carbonyl groups such as quinone, aryl-oe-carbonyl and cinnamaldehyd structures, leading to an elimination of the chromophoric structures without any substantial dissolution of lignin. In this part of work we have elucidated the kinetic behavior and the reaction products from lignin model compounds of the aryl-of- carbonyl and cinnamaldehyde types.1,2-Diarylpropan-1,3,-diol structures constitute an important building unit in native lignins. We have demonstrated that under hydrogen peroxide bleaching conditions the model compound 2,3--bis(4-hydroxy-3-methoxyphenyl)-3-ethoxy-propanol was converted to stilbenes, ûe. structures which when present in pulps may contribute to a rapid yellowing. The results obtained with model compounds under simulated lignin retaining bleaching conditions demonstrate that there are possibilities to improve the bleaching of mechanical pulps with hydrogen peroxide if:A. The remaining heavy metal ions complexed with DTPA are present in their lowest valence states.B. The concentration of hydroperoxy ions can be maintained at a high level at the lowest possible pH-value.

  • 18.
    Agrawal, Santosh
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martinez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marcos, Rocio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Readily Available Ruthenium Complex for Efficient Dynamic Kinetic Resolution of Aromatic alpha-Hydroxy Ketones2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 8, 2256-2259 p.Article in journal (Refereed)
    Abstract [en]

    A ruthenium complex formed from commercially available [Ru(p-cymene)Cl-2](2) and 1,4-bis(diphenylphosphino)butane catalyzes the racemization of aromatic alpha-hydroxy ketones very efficiently at room temperature. The racemization is fully compatible with a kinetic resolution catalyzed by a lipase from Pseudomonas stutzeri. This is the first example of dynamic kinetic resolution of alpha-hydroxy ketones at ambient temperature in which the metal and enzyme catalysts work in concert in one pot at room temperature to give quantitative yields of esters of alpha-hydroxy ketones with very high enantioselectivity.

  • 19.
    Ahlford, Katrin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric transfer hydrogenation of ketones: Catalyst development and mechanistic investigation2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The development of ligands derived from natural amino acids for asymmetric transfer hydrogenation (ATH) of prochiral ketones is described herein. In the first part, reductions performed in alcoholic media are examined, where it is found that amino acid-derived hydroxamic acids and thioamides, respectively, are simple and versatile ligands that in combination with [RhCp*Cl2]2 efficiently catalyze this particular transformation. Selectivities up to 97% ee of the corresponding secondary alcohols are obtained, and it is furthermore observed that the two different ligand classes, albeit based on the same amino acid scaffold, give rise to products of opposite configuration.

    The highly interesting enantioswitchable nature of the two abovementioned catalysts is studied in detail by mechanistic investigations. A structure/activity correlation analysis is performed, which reveals that the diverse behavior of the catalysts arise from different interactions between the ligands and the metal. Kinetic studies furthermore stress the catalyst divergence, since a difference in the rate determining step is established from initial rate measurements. In addition, rate constants are determined for each step of the overall reduction process.

    In the last part, catalyst development for ATH executed in water is discussed. The applicability of hydroxamic acid ligands is further extended, and catalysts based on these compounds are found to be efficient and compatible with aqueous conditions. The structurally even simpler amino acid amide is also evaluated as a ligand, and selectivities up to 90% ee are obtained in the reduction of a number of aryl alkyl ketones. The very challenging reduction of dialkyl ketones is moreover examined in the Rh-catalyzed aqueous ATH, where a modified surfactant-resembling sulfonylated diamine is used as ligand, and the reaction is carried out in the presence of SDS-micelles. A positive effect is to some extent found on the catalyst performance upon addition of phase-transfer components, especially regarding the catalytic activity in the reduction of more hydrophobic substrates.

  • 20.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Amino acid-derived amides and hydroxamic acids as ligands for asymmetric transfer hydrogenation in aqueous media2011In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 12, no 12, 1118-1121 p.Article in journal (Refereed)
    Abstract [en]

    Amides and hydroxamic acids derived from α-amino acids were evaluated as ligands in combination with rhodium and iridium half-sandwich complexes in asymmetric transfer hydrogenation (ATH) of ketones. The reactions were performed in aqueous media using lithium formate as hydride source. The catalyst systems turned out to be highly efficient and ees up to 90% were obtained.

  • 21.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Amino Acid Derived Rhodium Complexes: On the Origin of Enantioselectivity and Enantioswitchability2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 42, 11197-11209 p.Article in journal (Refereed)
    Abstract [en]

    Amino acid based thioamides, hydroxamic acids, and hydrazides have been evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. Catalysts containing thioamide ligands derived from L-valine were found to selectively generate the product with an R configuration (95 % ee), whereas the corresponding L-valine-based hydroxamic acids or hydrazides facilitated the formation of the (S)-alcohols (97 and 91 % ee, respectively). The catalytic reduction was examined by performing a structure–activity correlation investigation with differently functionalized or substituted ligands and the results obtained indicate that the major difference between the thioamide and hydroxamic acid based catalysts is the coordination mode of the ligands. Kinetic experiments were performed and the rate constants for the reduction reactions were determined by using rhodium–arene catalysts derived from amino acid thioamide and hydroxamic acid ligands. The data obtained show that the thioamide-based catalyst systems demonstrate a pseudo-first-order dependence on the substrate, whereas pseudo-zero-order dependence was observed for the hydroxamic acid containing catalysts. Furthermore, the kinetic experiments revealed that the rate-limiting steps of the two catalytic systems differ. From the data obtained in the structure–activity correlation investigation and along with the kinetic investigation it was concluded that the enantioswitchable nature of the catalysts studied originates from different ligand coordination, which affects the rate-limiting step of the catalytic reduction reaction.

  • 22.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric transfer hydrogenation of ketones catalyzed by amino acid derived rhodium complexes: on the origin of enantioselectivity and enantioswitchability: Corrigendum to vol 15(2009) 42, pp. 11197-2010In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, no 35, 10610-10610 p.Article in journal (Refereed)
  • 23.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lind, Jesper
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Mäler, Lena
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalyzed asymmetric transfer hydrogenation of alkyl and aryl ketones in aqueous media2008In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 10, no 8, 832-835 p.Article in journal (Refereed)
    Abstract [en]

    A novel lipophilic rhodium catalyst was evaluated in the enantioselective transfer hydrogenation of ketones in water using sodium formate as the hydride donor, and in the presence of sodium docecylsulfonate. Alkyl alkyl ketones were reduced in good yields and in moderate to good enantioselectivities, and the reduction of aryl alkyl ketones proceeded with excellent enantioselectivity (up to 97% ee).

  • 24.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Livendahl, Madeleine
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fine-tuning catalytic activity and selectivity-[Rh(amino acid thioamide)] complexes for efficient ketone reduction2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1873-3581, Vol. 50, no 46, 6321-6324 p.Article in journal (Refereed)
    Abstract [en]

    Amino acid-derived thioamides are prepared and evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. It is found that increasing the steric bulk at the C-terminus of the ligand had a positive impact on both activity and selectivity in the reduction reaction. In order to find the optimum catalyst, a study is performed on a series of thioamide ligands having substituents of varying size.

  • 25.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordin, Mikael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanistic investigation of enantioswitchable catalysts for asymmetric transfer hydrogenation2010In: Abstracts of Papers, 239th ACS National Meeting, San Francisco , CA, United States, March 21-25, 2010, Washington: American Chemical Society , 2010Conference paper (Other academic)
  • 26.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Simple and Efficient Catalyst System for the Asymmetric Transfer Hydrogenation of Ketones2007In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 16, 2541-2544 p.Article in journal (Refereed)
  • 27.
    Ahlgren, Joakim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Reitzel, Kasper
    Danielsson, Rolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Gogoll, Adolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Rydin, Emil
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006In: Water Research, no 40, 3705-3712 p.Article in journal (Refereed)
  • 28.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Waldebäck, Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sediment Depth Attenuation of Biogenic Phosphorus Compounds Measured by 31P NMR2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 3, 867-872 p.Article in journal (Refereed)
    Abstract [en]

    Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

  • 29.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Nielsen, T E
    Le Quement, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    An experimental and theoretical study of the mechanism of stannylcupration of alpha, beta-acetylenic ketones and esters2006In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, no 10, 2866-2873 p.Article in journal (Refereed)
    Abstract [en]

    The title reaction has been investigated by experimental and computational (DFT) techniques, and subsequently compared to the corresponding carbocupration reaction, with particular emphasis oil the stereoselectivity. For stannylcupration of an ynone substrate, only the anti-addition product is observed, whereas for the corresponding ynoate substrate, the stereoselectivity can be affected by the reaction conditions: in the presence of methanol as proton donor, the initial syn-addition product can be trapped, whereas a syn/anti mixture is obtained in a non-protic solvent. This is in sharp contrast to the carbocupration of the same ynone substrate with a cyanocuprate (RCu(CN)Li), which is highly selective for syn-addition. The product selectivities can be understood from a detailed computational characterization of the reaction paths, and in particular from the relative stabilities of the vinyl cuprate and allenolate intermediates. It is suggested that the stereodetermining step is protonation of vinyl cuprate intermediates.

  • 30.
    Ahlsten, Nanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalysed enol formation from allylic alcohols: Isomerisation, C−C and C−F bond formations 2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the isomerisation of allylic alcohols into enols and enolates catalysed by transition metal complexes. The transformation has been used to prepare both unsubstituted and α-substituted carbonyl compounds. Significant attention has been given to the mechanistic aspects of the reactions.

    In the first part of this thesis, an environmentally benign procedure for the redox isomerisation of allylic alcohols into ketones is described. The reaction takes place in water and at room temperature using a cationic rhodium complex in combination with water-soluble phosphines. A variety of allylic alcohols could be isomerised in high yields using this procedure.

    The second part describes the combination of an allylic alcohol isomerisation with a C−C bond formation, catalysed by a rhodium complex. In this way, allylic alcohols were coupled with aldehydes and N-tosyl imines forming aldol and Mannich-type products. In addition, homoallylic and bishomoallylic alcohols were for the first time isomerised into the corresponding enolates and coupled using this methodology.

    In the third part of this thesis, the isomerisation of allylic alcohols was coupled with a C−F bond formation using an iridium complex and electrophilic fluorinating reagents. This novel transformation was used to convert allylic alcohols into single regioisomers of α-fluoroketones. The reaction is tolerant to air and water and takes place at room temperature.

    All of the reactions described take place under mild conditions, are operationally simple, and utilise catalysts formed in situ from commercially available metal complexes and ligands.

  • 31.
    Ahlsten, Nanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalysed isomerisation of allylic alcohols: Applications to C−C, C−F and C−Cl bond formation2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The focus of this thesis has been to develop selective and atom-economical methods for carbon-carbon and carbon-heteroatom bond formation, and to some extent improve on existing findings in this area. More specifically, methods for the catalytic generation of enolates from allylic alcohols and their in situ functionalisation with electrophilic reagents are described.  

    In the first part of this thesis, a method for the Rh-catalysed redox-isomerisation of allylic alcohols into carbonyl compounds under environmentally benign conditions is described. The reaction takes place at room temperature, in the absence of acids or bases, using water as the only solvent, and it is applicable to both primary and secondary allylic alcohols.

    The second part describes the combination of an isomerisation reaction of allylic alcohols with a C−C bond formation, catalysed by a rhodium complex. In this way, allylic alcohols were coupled with aldehydes and N-tosylimines to give aldol and Mannich-type products. In addition to allylic alcohols, homoallylic and bishomoallylic alcohols could be used as enolate precursors, and this is the first report where the latter two substrate types have been used in such a reaction.       

    In the remaining parts of the thesis, an iridium-catalysed isomerisation of allylic alcohols has been combined with an electrophilic halogenation step to provide a conceptually new method for the synthesis of α-halogenated carbonyl compounds. In this way, α-fluoro and α-chloroketones have been synthesised as single constitutional isomers, with the regiochemistry of the final products determined by the position of the double bond in the allylic alcohols. The reactions are tolerant to air, run in water-organic solvent mixtures, and proceed at room temperature.

  • 32.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Agrawal, Santosh
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A facile synthesis of α-fluoro ketones catalyzed by [Cp*IrCl2](2)2011In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 16, 2600-2608 p.Article in journal (Refereed)
    Abstract [en]

    Allylic alcohols are isomerized into enolates (enols) by [Cp*IrCl2]2. The enolates react with Selectfluor present in the reaction media. This method produces α-fluoro ketones as single constitutional isomers in high yields.

  • 33.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Allylic alcohols as synthetic enolate equivalents: Isomerisation and tandem reactions catalysed by transition metal complexes2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 6, 1660-1670 p.Article in journal (Refereed)
    Abstract [en]

    Allylic alcohols can be isomerised into carbonyl compounds by transition metal complexes. In the last few years, catalyst design and development have resulted in highly efficient isomerisations under mild reaction conditions, including enantioselective versions. In addition, the isomerisation of allylic alcohols has been combined with C-C bond forming reactions when electrophiles such as aldehydes or imines were present in the reaction mixture. Also, C-F bonds can be formed when electrophilic fluorinating reagents are used. Thus, allylic alcohols can be treated as latent enol(ate)s. In this article, we highlight the latest developments concerning the isomerisation of allylic alcohols into carbonyl compounds, focusing in particular on tandem isomerisation/C-C or C-heteroatom bond formation processes. Significant attention is given to the mechanistic aspects of the reactions.

  • 34.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo-Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of α-chlorinated ketones and aldehydes: Iridium-catalyzed tandem 1,3-H shift/chlorination of allylic alcoholsManuscript (preprint) (Other academic)
  • 35.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalysed isomerisation of allylic alcohols in water at ambient temperature2010In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 12, no 9, 1628-1633 p.Article in journal (Refereed)
    Abstract [en]

    An environmentally benign method for the transformation of allylic alcohols into carbonyl compounds is described. Using [Rh(COD(CH3CN)(2)]BF4 (2) in combination with 1,3,5-triaza-7-phosphaadamantane (PTA, 1) as the catalytic system in water results in a very fast redox isomerisation of a variety of secondary allylic alcohols at ambient temperature. Also, some primary allylic alcohols can be isomerised into the corresponding aldehydes. The active complex, which in some cases can be used in catalyst loadings as low as 0.5 mol%, is formed in situ from commercially available reagents. Based on deuterium labelling studies, a tentative mechanism involving metal-enone intermediates is presented.

  • 36.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ir-catalysed formation of C-F bonds. From allylic alcohols to α-fluoroketones2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 29, 8331-8333 p.Article in journal (Refereed)
    Abstract [en]

    A novel iridium-catalysed tandem isomerisation/C-F bond formation from allylic alcohols and Selectfluor® to prepare α-fluorinated ketones as single constitutional isomers is reported.

  • 37.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalysed coupling of allylic, homoallylic, and bishomoallylic alcohols with aldehydes and N-tosylimines2010In: Abstracts of Papers, 239th ACS National Meeting, San Francisco, CA, United States, March 21-25, 2010, American Chemical Society , 2010Conference paper (Other academic)
  • 38.
    Ahlsten, Nanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalysed coupling of allylic, homoallylic, and bishomoallylic alcohols with aldehydes and N-tosylimines: insights into the mechanism2009In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 351, no 16, 2657-2666 p.Article in journal (Refereed)
    Abstract [en]

    The isomerisation of alkenols followed by reaction with aldehydes or N-tosylimines catalysed by rhodium complexes has been studied. The catalytically active rhodium complex is formed in situ from commercially available (cyclooctadiene)rhodium(l) chloride dimer [Rh(COD)Cl](2). The tandem process affords aldol and Mannich-type products in excellent yields. The key to the success of the coupling reaction is the activation of the catalysts by reaction with postassium tert-butoxide (t-BuOK), which promotes a catalytic cycle via alkoxides rather than rhodium hydrides. This mechanism minimises the formation of unwanted by-products. The mechanism has been studied by (1)H NMR spectroscopy and deuterium labelling experiments.

  • 39. Ahmad, Anees
    et al.
    Scarassati, Paulo
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Universidade de São Paulo, Brazil.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Silva, Luiz F., Jr.
    Oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III)2013In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 54, no 43, 5818-5820 p.Article in journal (Refereed)
    Abstract [en]

    A novel protocol for the oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III) was developed. This approach uses inexpensive, readily available, and stable chemicals (PhI, mCPBA, and TsOH) giving rearrangement products in yields comparable to those obtained using the more expensive commercially available [hydroxy(tosyloxy)iodo]benzene [HTIB or Koser's reagent]. Additionally, an alternative protocol for the synthesis of 1-methyl-2-tetralone through the one-step epoxidation/rearrangement of 4-methyl-1,2-dihydronaphthalene using mCPBA and TsOH was developed.

  • 40. Ai, Yue-Jie
    et al.
    Liao, Rong-zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Shu-feng
    Luo, Yi
    Fang, Wei-Hai
    Theoretical Studies on Photoisomerizations of (6-4) and Dewar Photolesions in DNA2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 44, 14096-14102 p.Article in journal (Refereed)
    Abstract [en]

    The (6-4) photoproduct ((6-4) PP) is one of the main lesions in UV-induced DNA damage. The (6-4) PP and its valence isomer Dewar photoproduct (Dewar PP) can have a great threat of mutation and cancer but gained much less attention to date. In this study, with density functional theory (DFT) and the complete active space self-consistent field (CASSCF) methods, the photoisomerization processes between the (6-4) PP and the Dewar PP in the gas phase, the aqueous solution, and the photolyase have been carefully examined. Noticeably, the solvent effect is treated with the CASPT2//CASSCF/Amber (QM/MM) method. Our calculations show that the conical intersection (Cl) points play a crucial role in the photoisomerization reaction between the (6-4) PP and the Dewar PP in the gas and the aqueous solution. The ultrafast internal conversion between the S-2 ((1)pi pi*) and the So states via a distorted intersection point is found to be responsible for the formation of the Dewar PP lesion at 313 nm, as observed experimentally. For the reversed isomeric process, two channels involving the "dark" excited states have been identified. In addition to the above passages, in the photolyase, a new electron-injection isomerization process as an efficient way for the photorepair of the Dewar PP is revealed.

  • 41. Aili, Daniel
    et al.
    Enander, Karin
    Rydberg, Johan
    Lundström, Ingemar
    Baltzer, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Biochemistry and Organic Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II.
    Liedberg, Bo
    Aggregation-Induced Folding of a de novo Designed Polypeptide Immobilized on Gold Nanoparticles2006In: J. Am. Chem. Soc., no 128, 2194-2195 p.Article in journal (Refereed)
  • 42. Aili, Daniel
    et al.
    Enander, Karin
    Rydberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II.
    Nesterenko, Irina
    Björefors, Fredrik
    Baltzer, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II.
    Liedberg, Bo
    Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles2008In: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 130, no 17, 5780-5788 p.Article in journal (Refereed)
    Abstract [en]

    Reversible assembly of gold nanoparticles controlled by the homodimerization and folding of an immobilized de novo designed synthetic polypeptide is described. In solution at neutral pH, the polypeptide folds into a helix-loop-helix four-helix bundle in the presence of zinc ions. When immobilized on gold nanoparticles, the addition of zinc ions induces dimerization and folding between peptide monomers located on separate particles, resulting in rapid particle aggregation. The particles can be completely redispersed by removal of the zinc ions from the peptide upon addition of EDTA. Calcium ions, which do not induce folding in solution, have no effect on the stability of the peptide decorated particles. The contribution from folding on particle assembly was further determined utilizing a reference peptide with the same primary sequence but containing both D and L amino acids. Particles functionalized with the reference peptide do not aggregate, as the peptides are unable to fold. The two peptides, linked to the nanoparticle surface via a cysteine residue located in the loop region, form submonolayers on planar gold with comparable properties regarding surface density, orientation, and ability to interact with zinc ions. These results demonstrate that nanoparticle assembly can be induced, controlled, and to some extent tuned, by exploiting specific molecular interactions involved in polypeptide folding.

  • 43.
    Alam, Rauful
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-catalyzed Allylic C-H and C-OH Functionalization. Reactions of the Obtained Allylboronic Acids2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis is focused on the studies of two major transformations. The first transformation deals with the development of palladium-catalyzed selective allylic trifluoroacetoxylation reactions based on C-H functionalization, whereas the second comprises the synthesis and isolation of allylboronic acids using diboronic acid B2(OH)4 as boron source. Both reactions proceed with a very high regio- and stereoselectivity. The mechanistic studies of the allylic C-H trifluoroacetoxylation indicate that the reaction proceeds via (η3-allyl)palladium intermediate.

    The reactivity of the allylboronic acids was studied with ketone and imine substrates. Unlikeother boronates (such as allyl-Bpin derivatives), allylboronic acids react with ketones and imines without any additives under neutral and mild conditions (typically at room temperature). The regio- and stereoselectivity of this reaction is remarkably high. Using functionalized allylboronic acids (prepared in the above mentioned Pd-catalyzed reactions) homoallylic alcohols and amines with adjacent tertiary and quaternary centers could be obtained with high selectivity. Interestingly, both the ketones and the imines reacted with anti-stereoselectivity. This was surprising for the imines. Our mechanistic study has shown that the acyclic aldimines undergo cis/trans isomerization prior to the allylation reaction.

  • 44.
    Alam, Rauful
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Regio- and Stereoselective Reactions for the Synthesis of Allylic and Homoallylic Compounds2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on two main areas of organic synthesis, palladium-catalyzed functionalization of alkenes and allylic alcohols, as well as development of new allylboration reactions.

    We have developed a palladium-catalyzed selective allylic trifluoroacetoxylation reaction based on C−H functionalization. Allylic trifluoroacetates were synthesized from functionalized olefins under oxidative conditions. The reactions proceed under mild conditions with a high level of diastereoselectivity. Mechanistic studies of the allylic C−H trifluoroacetoxylation indicate that the reaction proceeds via (η3-allyl)palladium(IV) intermediate.

    Palladium-catalyzed regio- and stereoselective synthesis of allylboronic acids from allylic alcohols has been demonstrated. Diboronic acid B2(OH)4 was used as the boron source in this process.

    The reactivity of the allylboronic acids were studied in three types of allylboration reactions: allylboration of ketones, imines and acyl hydrazones. All three processes are conducted under mild conditions without any additives. The reactions proceeded with remarkably high regio- and stereoselectivity.

    An asymmetric version of the allylboration of ketones was also developed. In this process chiral BINOL derivatives were used as catalysts. The reaction using γ-disubstituted allylboronic acids and various aromatic and aliphatic ketones afforded homoallylic alcohols bearing two adjacent quaternary stereocenters with excellent regio-, diastereo- and enantioselectivity (up to 97:3 er) in high yield. The stereoselectivity in the allylboration reactions could be rationalized on the basis of the Zimmerman-Traxler TS model.

  • 45.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Das, Arindam
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Huang, Genping
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereoselective allylboration of imines and indoles under mild conditions. An in situ E/Z isomerization of imines by allylboroxines2014In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 5, no 7, 2732-2738 p.Article in journal (Refereed)
    Abstract [en]

    Direct allylboration of various acyclic and cyclic aldimine, ketimine and indole substrates was performed using allylboronic acids. The reaction proceeds with very high anti-stereoselectivity for both E and Z imines. The allylboroxines formed by dehydration of allylboronic acids have a dual effect: promoting E/Z isomerization of aldimines and triggering the allylation by efficient electron withdrawal from the imine substrate.

  • 46.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mihai, Raducan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Szabo, Kalman J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Formation of Adjacent Stereocenters by Allylboration of Ketones under Mild Neutral Conditions2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 10, 2546-2549 p.Article in journal (Refereed)
    Abstract [en]

    Allylboronic acids readily react with a broad variety of ketones, affording homoallylic alcohols with adjacent quaternary and tertiary stereocenters. The reaction proceeds with very high anti stereoselectivity even if the substituents of the keto group have a similar size. a-Keto acids react with syn stereoselectivity probably due to the formation of acyl boronate intermediates. The allylation reactions proceed without added acids/bases under mild conditions. Because of this, many functionalities are tolerated even with in situ generated allylboronic acids.

  • 47.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pilarski, Lukasz T.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabo, Kalman J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereoselective intermolecular allylic C-H trifluoroacetoxylation of functionalized alkenes2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 21, 8778-8781 p.Article in journal (Refereed)
    Abstract [en]

    Pd-catalyzed allylic C-H trifluoroacetoxylation of substituted alkenes was performed using PhI(OCOCF3)(2) as the oxidant and acyloxy source. Trifluoroacetoxylation of monosubstituted cyclopentenes and cyclohexenes proceeds with excellent regio- and diastereoselectivity. Studies with one of the possible (eta(3)-allyl)Pd(II) intermediates suggest that the reaction proceeds via stereoselective formation of Pd(IV) intermediates and subsequent stereo- and regioselective reductive elimination of the product.

  • 48.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Raducan, Mihai
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diastereoselective allylboration of wide variety of carbonyl compounds using allylboronic acids: Construction of adjacent tertiary and quaternary centers2013In: Abstracts of papers of The American Chemical Society, American Chemical Society (ACS), 2013, Vol. 246, 364-ORGN- p.Conference paper (Refereed)
  • 49.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vollgraff, Tobias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Adjacent Quaternary Stereocenters by Catalytic Asymmetric Allylboration2015In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, no 35, 11262-11265 p.Article in journal (Refereed)
    Abstract [en]

    Allylboration of ketones with gamma-disubstituted allylboronic acids is performed in the presence of chiral BINOL derivatives. The reaction is suitable for single-step creation of adjacent quaternary stereocenters with high selectivity. We show that, with an appropriate choice of the chiral catalyst and the stereoisomeric prenyl substrate, full control of the stereo- and enantioselectivity is possible in the reaction.

  • 50.
    Alamsetti, Santosh Kumar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andreas K. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Intramolecular Hydroamination of Propargylic Carbamates and Carbamothioates2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 5, 1434-1437 p.Article in journal (Refereed)
    Abstract [en]

    An efficient and simple methodology was developed for the synthesis of oxazolidinones, oxazolidinthiones, imidazolidinthiones, and imidazolidinones from the corresponding propargylic starting materials using Pd(OAc)(2) and n-Bu4NOAc as catalysts in DCE at room temperature.

1234567 1 - 50 of 2402
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