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Oxidative gold catalysis

The utility of aryltrimethylsilanes 1 as coupling partners in oxidative gold catalysis has been established through the development of first- and second-generation methodologies for alkene oxyarylation, and through the realisation of a protocol for the direct arylation of simple arenes. Oxidative oxyarylation of mono-substituted olefins 2 is achieved in the presence of a commercially-available precatalyst, Ph3P AuCl and a fluoronium oxidant, Selectfluor. The net addition of an O-nuc leophile and a silane-derived aryl moiety across the C=C double bond affords the conesponding homo benzylic alcohol derivative 3 with complete regioselectivity. Although diverse O-nucleophiles and arylating agents are tolerated, the substrate-scope is limited to alkenes bearing a single alkyl substituent due to the high reactivity of the oxidant. Relative to literature procedures employing arylboronic acids, the use of arylsilanes 1 significantly reduces the generation of symmetrical biaryls 4 via oxidative homocoupling of the arylating agent. Limitations imposed upon the first-generation protocol by Selectfluor prompted an extensive screen of reaction conditions that led to identification of l -hydroxy-I,2-benziodoxol-3-(lH)-one (IBA) as an efficient terminal oxidant for gold-catalysed oxyarylation. Use of IBA expands the substrate scope to include styrenes 5, thereby providing access to bibenzyls 6, and gem-disubstituted olefins 7, which afford tertiary homobenzylic alcohol derivatives 8. Whilst the range of suitable O-nucleophiles is largely resh'icted to methanol, sterically- and electronically-diverse arylsilanes 1 can be employed. Use of benzotrifluoride as the reaction solvent substantially reduces the generation of alylsilane homocoupling side-products 4.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649363
Date January 2014
CreatorsBall, Liam Thomas
PublisherUniversity of Bristol
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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