Involvement of an Oxidation-Reduction Equilibrium in Chromium-Mediated Enantioselective Nozaki–Hiyama Reactions

Autor:	Martin W. G. de Bolster, Henri Stephan Schrekker, Csongor Hajdu, Károly Micskei, Ludger A. Wessjohann, Tamás Patonay
Rok vydání:	2004
Předmět:	Chromium Meerwein–Ponndorf–Verley reduction Enantiopure drug Nucleophile Ligand Chemistry Enantioselective synthesis Oppenauer oxidation chemistry.chemical_element Organic chemistry General Chemistry Enantiomeric excess
Zdroj:	Advanced Synthesis & Catalysis. 346:731-736
ISSN:	1615-4169 1615-4150
DOI:	10.1002/adsc.200404021
Popis:	Ligand induced enantioselective versions of the chromium(II)-mediated Nozaki–Hiyama reaction to homoallyl alcohols proved to be very difficult to achieve, especially if any other nucleophile than the parent allylchromium(III) species was applied. Also, the reaction is frequently accompanied by the formation of oxidation side products, predominantly allyl ketones. This can be explained by an Oppenauer–(Meerwein–PonndorfVerley) type mechanism (OMPV reaction). The addition of an enantiopure ligand to racemic chromium homoallyl alcoholate intermediates produced enantiomerically enriched homoallyl alcohols with an enantiomeric excess of up to 32%. This observation not only supports that the proposed OMPV oxidation-reduction equilibrium plays a crucial role in Nozaki–Hiyama reactions, but also proves its involvement in enantioselective versions.
Databáze:	OpenAIRE
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