Gupta V, Sudhir V S, Mandal T, Schneider C * Universität Leipzig, Germany
Organocatalytic, Highly Enantioselective Vinylogous Mukaiyama-Michael Reaction of
Acyclic Dienol Silyl Ethers.
Angew. Chem. Int. Ed. 2012;
51: 12609-12612
Key words
vinylogous Mukaiyama–Michael reaction - Jørgensen–Hayashi catalyst - enals - dienol
silyl ethers
Significance
The authors report a highly enantio- and diastereoselective vinylogous Mukaiyama–Michael
reaction of acylic dienol silyl ethers 2 to various enals 1 by employing a Jørgensen–Hayashi catalyst. 1,7-Dicarbonyl compounds 3 are obtained under mild reaction conditions with good to excellent yield and remarkable
regioselectivity. Z/E-Configured γ-methyl-substituted dienol silyl ethers are selectively converted into
the anti and syn products 3 with excellent enantioselectivity.
Comment
Vinylogous Michael reactions of dienol derivatives can form a C–C bond with high regio-
and stereoselectivity in the presence of a chiral catalyst. However, a catalytic enantioselective
process of this reaction with acyclic nucleophiles and enals was elusive since the
reaction can produce a number of regio- and stereoisomers. Herein, the catalyst nicely
operates presumably by forming an imminium species with enal 1 to induce 1,4-addition of nucleophile 2 with high γ-selectivity.
