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Reactions of a Stable (Phosphanyl)(silyl)carbene with Aliphatic Aldehydes: [2+1] versus [2+2] Addition to a Carbonyl Group
Author(s) -
Illa Ona,
Gornitzka Heinz,
Branchadell Vicenç,
Baceiredo Antoine,
Bertrand Guy,
Ortuño Rosa M.
Publication year - 2003
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200300226
Subject(s) - chemistry , carbene , silylation , diastereomer , cycloaddition , alkyl , medicinal chemistry , reaction mechanism , stereochemistry , catalysis , organic chemistry
The reactions between the stable (phosphanyl)(silyl)carbene 1 and different aliphatic aldehydes have been investigated for the first time. Results reveal that two competitive processes take place. The kinetically most favorable one is a concerted [2+1] cycloaddition to carbonyl leading to oxiranes as single diastereomers, with the trans arrangement of the alkyl and phosphoranyl groups, as the major products. Simultaneously, a [2+2]‐like addition provides short‐lived oxaphosphetene intermediates that rapidly evolve to the corresponding olefins with E stereochemistry, which are the thermodynamically most stable compounds. DFT calculations establish the mechanism for both processes and a rationale for the observed diastereoselectivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)