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Ruthenium-catalyzed C-H Functionalization of (Hetero)arenes
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerned about the Ru-catalyzed C-H functionalizations on the synthesis of 2-arylindole unit, silylation of heteroarenes and preparation of aryne precursor.

In the first project, we developed the Ru-catalyzed C2-H arylation of N-(2-pyrimidyl) indoles and pyrroles with nucleophilic arylboronic acids under oxidative conditions. Wide variety of arylboronic acids afforded the desired product in excellent yield regardless of the substituents or functional group electronic nature. Electron-rich heteroarenes are well suited for this method than electron-poor heteroarenes. Halides such as bromide and iodide also survived, further derivatisation of the halide is shown by Heck alkenylation. In order to find catalytic on-cycle intermediate extensive mechanistic experiments have been carried out by preparing presumed ruthenacyclic complexes and C-H/D exchange reactions. It suggested that para-cymene ligand is not present in the catalytic on-cycle intermediate and we suspect that metalation occurs with electrophilic ruthenium center via SEAr mechanism.

In the second project, we developed the Ru-catalyzed silylation of gramine, tryptamine and their congeners using silanes as coupling partner. The transformation worked well with many different silanes. Regarding directing group, nitrogen atom containing directing groups are more favoured than the oxygen containing directing groups. Wide range of gramines and tryptamines also yielded the desired product in poor to excellent yield. At higher temperature, albeit in low yield, undirected silylation occurred. In order to get some insights about the reaction pathway of the silylation C-H/D exchange experiments were performed, and it revealed the possibility of C4-H activation of gramines by an electron rich metal- Si-H/D experiments showed Si-H activation by Ru is easy.

In the final project, we presented the closely related aryne precursors from arylboronic acids via Ru-catalyzed C-H silylation of arylboronates and their selective oxidation. Worthy of note, the aryne capture products obtained from arylboronic acids in a single purification.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , p. 59
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1465
Keywords [en]
catalysis, C-H activation, heterocycles, ruthenium, aryne precursor, silylation, gramine
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-310998ISBN: 978-91-554-9783-5 (print)OAI: oai:DiVA.org:uu-310998DiVA, id: diva2:1058355
Public defence
2017-02-24, B22, BMC, Husargatan 3, Uppsala, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2017-02-03 Created: 2016-12-20 Last updated: 2017-02-07
List of papers
1. Ru-Catalysed C-H Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies
Open this publication in new window or tab >>Ru-Catalysed C-H Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies
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2015 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 14, p. 5380-5386Article in journal (Refereed) Published
Abstract [en]

The Ru-catalysed C2-H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on-cycle intermediates do not possess a para-cymene ligand and that the on-cycle metalation occurs through an electrophilic attack by the Ru centre.

Keywords
catalysis, C-H activation, heterocycles, reaction mechanisms, ruthenium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-252711 (URN)10.1002/chem.201405931 (DOI)000352504500017 ()25689052 (PubMedID)
Funder
Swedish Research Council
Available from: 2015-05-18 Created: 2015-05-11 Last updated: 2017-12-04Bibliographically approved
2. Ru-Catalysed C-H Silylation of Gramines, Tryptamines and their Congeners
Open this publication in new window or tab >>Ru-Catalysed C-H Silylation of Gramines, Tryptamines and their Congeners
2016 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, no 34, p. 5868-5871Article in journal (Refereed) Published
Abstract [en]

Selective Ru-catalysed C2–H silylation of heteroarenes is presented. The transformation works with or without directing group assistance and requires no protecting groups. Gramines and tryptamines may be converted efficiently whilst avoiding deleterious elimination side-reactions. Mechanistic studies reveal an unusual activation of the indole C4–H bond by an electron-rich metal.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-286545 (URN)10.1039/C6CC00803H (DOI)000374396500022 ()27050747 (PubMedID)
Funder
Swedish Research Council
Available from: 2016-04-20 Created: 2016-04-20 Last updated: 2017-11-30Bibliographically approved
3. Synthesis of aryne precursors via transition metal-catalyzed C-H silylation
Open this publication in new window or tab >>Synthesis of aryne precursors via transition metal-catalyzed C-H silylation
2014 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal, Meeting abstract (Other academic) Published
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-247860 (URN)000349167403600 ()
Conference
248th National Meeting of the American-Chemical-Society (ACS), AUG 10-14, 2014, San Francisco, CA
Available from: 2015-03-26 Created: 2015-03-24 Last updated: 2017-12-04Bibliographically approved

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