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  • 51.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Somfai, Peter
    Royal Institute of Technology, Sweden.
    A regio- and stereodivergent route to all isomers of vic-amino alcohols2002In: Latvijas Journal of Chemistry, ISSN 0868-8249, Vol. 1, p. 69-78Article in journal (Refereed)
  • 52.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Somfai, Peter
    Royal Institute of Technology, Sweden.
    A regio- and stereodivergent route to all isomers of vic-amino alcohols2002In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 67, no 24, p. 8574-8583Article in journal (Refereed)
    Abstract [en]

    Vicinal amino alcohols are substructures in several important natural products. They are also frequently employed ligands in asymmetric synthesis. Many enantioselective syntheses of vic-amino alcohols have been reported, but each structure has required its own synthetic route. This study presents a synthetic strategy leading to all eight possible isomers of a given beta-amino alcohol, starting from vinyl epoxides. The developed strategy focuses on the propensity of vinyl epoxides and vinylaziridines to be selectively ring-opened at the allylic position by suitable hard nucleophiles. Within this strategy, a novel large-scale aminolysis reaction and the synthesis of a trisubstituted N-H vinylaziridine are detailed.

  • 53.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Somfai, Peter.
    Royal Institute of Technology, Sweden.
    Determination of the relative configuration of vic-amino alcohols2003In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 44, no 6, p. 1279-1281Article in journal (Refereed)
    Abstract [en]

    A large set of syn- and anti-1,2-amino alcs. has been synthesized. Upon comparison of the CHO and CHN 1H NMR shifts a general trend has been obsd., making it possible to det. the relative configuration of 1,2-amino alcs. without derivatization or shift reagents.

  • 54.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Somfai, Peter
    Royal Institute of Technology, Sweden.
    Divergent Synthesis of D-erythro-Sphingosine, L-threo-Sphingosine, and Their Regioisomers2003In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 68, no 6, p. 2514-2517Article in journal (Refereed)
    Abstract [en]

    Starting from a vinyl epoxide, a divergent synthesis of four sphingosine isomers is described. The remaining four isomers can easily be synthesized using the same methodol. Although numerous syntheses of sphingosine have been published, this is the first general route leading to all eight isomers in this important compd. class. The synthetic strategy relies on regioselective opening of a vinyl epoxide and a vinylaziridine in the allylic position.

  • 55.
    Olofsson, Berit
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Somfai, Peter
    Organisk kemi, KTH.
    Vinylepoxides in Organic Synthesis2006In: Aziridines and Epoxides in Organic Synthesis, Wiley-VCH: Weinheim , 2006, p. 315-347Chapter in book (Refereed)
    Abstract [en]

    Vinylepoxides have become important intermediates in organic synthesis. The main reason for this is the development of selective methods for their subsequent transformations. As vinylepoxides are a special type of allylic electrophiles, it is necessary to control both the regioselectivity and the diastereoselectivity in their reactions with nucleophiles. The practical usefulness of vinylepoxides in synthesis will, however, always be dictated by their availability. Several methods for the asymmetric preparation of vinyloxiranes have been developed and it can be expected that the use of these compounds in organic synthesis will increase. This chapter starts with a discussion of the available techniques for preparing vinylepoxides, with emphasis on asymmetric methods. In the second part various transformations of vinylepoxides are summarized.

  • 56.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Wijtmans, Roel
    Royal Institute of Technology, Sweden.
    Somfai, Peter.
    Royal Institute of Technology, Sweden.
    Synthesis of N-H vinylaziridines: a comparative study2002In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 58, no 30, p. 5979-5982Article in journal (Refereed)
    Abstract [en]

    Vinylaziridines are useful and versatile synthetic intermediates, as the relief of ring-strain provides a driving force for efficient ring-opening or ring-expansion reactions. Furthermore, the vinyl group can be derivatized into interesting functionalities. The ring-closure of vicinal amino alcs. constitutes a straightforward route to aziridines. Several methods exist for this transformation, although many cannot be applied to vinylaziridines due to their acid lability. This comparative study describes the most effective sequences for the formation of N-H vinylaziridines.

  • 57.
    Pace, Vittorio
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of Vienna, Austria.
    Holzer, Wolfgang
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview2014In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 356, no 18, p. 3697-3736Article, review/survey (Refereed)
    Abstract [en]

    The nucleophilic addition of carbon nucleophiles to amides has traditionally been a difficult task, both due to reactivity and selectivity problems. When successful, these processes would represent straightforward routes towards carbonyl-type or amine compounds, depending on the fate of the generated tetrahedral intermediate. The direct addition of nucleophiles to amides for the preparation of ketones has been studied and applied to the syntheses of several natural products. On the other hand, the addition of nucleophiles to amides to obtain substituted amines represented a major challenge, and only scattered applications on particular substrates have appeared. Initial improvements were based on the activation of amides by introduction of particular substituents, such as in N-methoxy amides (Weinreb amides) or electron-withdrawing groups able to increase the carbon nucleophilicity. Although these strategies facilitate the introduction of nucleophiles, chemoselectivity issues arise when additional electrophilic moieties (i.e., carbonyls) are present, thus decreasing the versatility of the methods. In recent years, important advancements towards fully chemoselective methods have been realized. The capture of tetrahedral intermediates with acids generates highly electrophilic iminium species able to undergo chemoselective additions of various nucleophiles, thus accessing substituted amines. Alternatively, the in situ generation of an iminium triflate ion allows highly chemoselective additions of nucleophiles, yielding amines, ketones or ketimines. Also thioamides can be used as precursors of ketones or alpha-substituted amines. The success of the above methodologies is further showcased by the application in various syntheses of natural products or biologically active molecules.

  • 58.
    Petersen, Tue B.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Khan, Rehan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-free synthesis of aryl esters from carboxylic acids and diaryliodonium salts2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 13, p. 3462-3465Article in journal (Refereed)
    Abstract [en]

    An efficient arylation of carboxylic acids with diaryliodonium salts has been developed, giving aryl esters in high yields within short reaction times for both arom. and aliph. substrates. The transition-metal-free conditions are compatible with a range of functional groups, and good chemoselectivity is obsd. with unsym. diaryliodonium salts.  Furthermore, steric hindrance in the ortho positions is well tolerated both in the carboxylic acid and in the diaryliodonium salt, yielding aryl esters that cannot be obtained via other esterification protocols.

  • 59.
    Purkait, Nibadita
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kervefors, Gabriella
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Linde, Erika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Regiospecific N-Arylation of Aliphatic Amines under Mild and Metal-Free Reaction Conditions2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 35, p. 11427-11431Article in journal (Refereed)
    Abstract [en]

    A transition metal-free N-arylation of primary and secondary amines with diaryliodonium salts is presented. Both acyclic and cyclic amines are well tolerated, providing a large set of N-alkyl anilines. The methodology is unprecedented among metal-free methods in terms of amine scope, the ability to transfer both electron-withdrawing and electron-donating aryl groups, and efficient use of resources, as excess substrate or reagents are not required.

  • 60.
    Reitti, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gurubrahamam, Ramani
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Walther, Melanie
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Phenols and Aryl Silyl Ethers via Arylation of Complementary Hydroxide Surrogates2018In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 20, no 7, p. 1785-1788Article in journal (Refereed)
    Abstract [en]

    Two transition-metal-free methods to access substituted phenols via the arylation of silanols or hydrogen peroxide with diaryliodonium salts are presented. The complementary reactivity of the two nucleophiles allows synthesis of a broad range of phenols without competing aryne formation, as illustrated by the synthesis of the anesthetic Propofol. Furthermore, silyl-protected phenols can easily be obtained, which are suitable for further transformations.

  • 61.
    Reitti, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Villo, Piret
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot C-H Functionalization of Arenes by Diaryliodonium Salts2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 31, p. 8928-8932Article in journal (Refereed)
    Abstract [en]

    A transition-metal-free, mild, and highly regioselective synthesis of nitroarenes from arenes has been developed. The products are obtained in a sequential one-pot reaction by nitration of iodine(III) reagents with two carbon ligands, which are formed in situ from iodine(I). This novel concept has been extended to formation of aryl azides, and constitutes an important step towards catalytic reactions with these hypervalent iodine reagents. An efficient nitration of isolated diaryl-iodonium salts has also been developed, and the mechanism is proposed to proceed by a [2,2] ligand coupling pathway.

  • 62. Silva, Luiz F., Jr.
    et al.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hypervalent iodine reagents in the total synthesis of natural products2011In: Natural product reports (Print), ISSN 0265-0568, E-ISSN 1460-4752, Vol. 28, no 10, p. 1722-1754Article, review/survey (Refereed)
    Abstract [en]

    This report describes the recent applications of hypervalent iodine reagents in the total synthesis of natural products. The large diversity of high-yielding and chemoselective reactions that can be achieved, even for highly functionalized molecules, is summarized, demonstrating that hypervalent iodine reagents have become an essential tool in synthetic organic chemistry.

  • 63. Siqueira, Fernanda A.
    et al.
    Ishikawa, Eloisa E.
    Fogaça, André
    Faccio, Andréa T.
    Carneiro, Vânia M. T.
    Soares, Rafael R. S.
    Utaka, Aline
    Tébéka, Iris R. M.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Silva Jr., Luiz F.
    Metal-Free Synthesis of Indanes by Iodine(III)-Mediated Ring Contraction of 1,2-Dihydronaphthalenes2011In: Journal of the Brazilian Chemical Society, ISSN 0103-5053, E-ISSN 1678-4790, Vol. 22, no 9, p. 1795-1807Article in journal (Refereed)
    Abstract [en]

    A metal-free protocol was developed to synthesize indanes by ring contraction of 1,2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser’s reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH3CN, 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH2Cl2) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1,3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry.

  • 64.
    Stridfeldt, Elin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Reitti, Marcus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Blid, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Norrby, Per-Ola
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Competing Pathways in O-Arylations with Diaryliodonium Salts: Mechanistic Insights2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 53, p. 13249-13258Article in journal (Refereed)
    Abstract [en]

    A mechanistic study of arylations of aliphatic alcohols and hydroxide with diaryliodonium salts, to give alkyl aryl ethers and diaryl ethers, has been performed using experimental techniques and DFT calculations. Aryne intermediates have been trapped, and additives to avoid by-product formation originating from arynes have been found. An alcohol oxidation pathway was observed in parallel to arylation; this is suggested to proceed by an intramolecular mechanism. Product formation pathways via ligand coupling and arynes have been compared, and 4-coordinated transition states were found to be favored in reactions with alcohols. Furthermore, a novel, direct nucleophilic substitution pathway has been identified in reactions with electron-deficient diaryliodonium salts.

  • 65.
    Stridfeldt, Elin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Seemann, Alexandra
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bouma, Marinus J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dey, Chandan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ertan, Anne
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis, Characterization and Unusual Reactivity of Vinylbenziodoxolones-Novel Hypervalent Iodine Reagents2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 45, p. 16066-16070Article in journal (Refereed)
    Abstract [en]

    A novel type of hypervalent iodine(III) reagents, vinylbenziodoxolones (VBX), has been synthesized in a one-pot reaction from 2-iodobenzoic acid. VBX is bench stable, has been thoroughly characterized and the cyclic structure is supported by X-ray analysis. The reactivity of VBX was investigated in vinylation of nitrocyclohexane, and delivered vinylated products with opposite regioselectivity compared to acyclic vinyl(aryl) iodonium salts. The reagents could become a powerful tool in vinylation reactions under both metal-free and metal-catalyzed conditions.

  • 66.
    Tinnis, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stellenbosch University, South Africa.
    Metal-Free N-Arylation of Secondary Amides at Room Temperature2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 11, p. 2688-2691Article in journal (Refereed)
    Abstract [en]

    The arylation of secondary acyclic amides has been achieved with diaryliodonium salts under mild and metal-free conditions. The methodology has a wide scope, allows synthesis of tertiary amides with highly congested aryl moieties, and avoids the regioselectivity problems observed in reactions with (diacetoxyiodo)benzene.

  • 67.
    Tolnai, Gergely L.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nilsson, Ulf J.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient O-Functionalization of Carbohydrates with Electrophilic Reagents2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 37, p. 11226-11230Article in journal (Refereed)
    Abstract [en]

    Novel methodology for O-functionalization of carbohydrate derivatives has been established using bench-stable and easily prepared iodonium(III) reagents. Both electron-withdrawing and electron-donating aryl groups were introduced under ambient conditions and without precautions to exclude air or moisture. Furthermore, the approach was extended both to full arylation of cyclodextrin, and to trifluoroethylation of carbohydrate derivatives. This is the first general approach to introduce traditionally non-electrophilic groups into any of the OH groups around the sugar backbone. The methodology will be useful both in synthetic organic chemistry and biochemistry, as important functional groups can be incorporated under simple and robust reaction conditions in a fast and efficient manner.

  • 68.
    Utas, Josefin E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient Synthesis of 2-Substituted Imidazoles by Palladium-Catalyzed Cross-Coupling with Benzylzinc Reagents2006In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 12, p. 1965-1967Article in journal (Refereed)
    Abstract [en]

    Substituted benzylzinc reagents have been used in novel cross-coupling reactions with 2-iodo imidazoles to form compounds containing both a phenol and an imidazole moiety. The ­intramolecular hydrogen-bonding properties of these compounds were subsequently studied.

  • 69.
    Villo, Piret
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of Tartu, Estonia.
    Kervefors, Gabriella
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Inside front cover2018Other (Other academic)
  • 70.
    Villo, Piret
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of Tartu, Estonia.
    Kervefors, Gabriella
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-free, chemoselective arylation of thioamides yielding aryl thioimidates or N-aryl thioamides2018In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, no 64, p. 8810-8813Article in journal (Refereed)
    Abstract [en]

    Reactions of secondary thioamides with diaryliodonium salts under basic, transition metal-free conditions resulted in chemoselective S-arylation to provide aryl thioimidates in good to excellent yields. Equimolar amounts of thioamide, base and diaryliodonium salt were sufficient to obtain a diverse selection of products within short reaction times. Reactions with thiolactams delivered N-arylated thioamides in good yield at room temperature.

  • 71.
    Zhu, Mingzhao
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot synthesis of diaryliodonium salts using toluenesulfonic acid - a fast entry to electron-rich diaryliodonium tosylates and triflates2008In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 4, p. 592-596Article in journal (Refereed)
    Abstract [en]

    A direct synthesis of symmetric and unsymmetric electron-rich diaryliodonium salts is described. The use of MCPBA and toluenesulfonic acid delivers diaryliodonium tosylates in high yields. An in situ anion exchange has also been developed, giving access to the corresponding triflate salts.

12 51 - 71 of 71
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