Lewis acid-promoted carbonyl addition of lithium (α- carbalkoxyvinyl)cuprates to aldehydes provides a novel asymmetric synthesis of β,β-disubstituted α-(hydroxyalkyl)acrylates
A new anionic addition process has been developed for the asymmetric synthesis of unusual Baylis-Hillman adducts, β,β-disubstituted α- (hydroxyalkyl)acrylates. The new process involves conjugate addition of R2CuLi to β-substituted α,β-acetylenic ester to give lithium (α- carbalkoxyvinyl)cuprate which was then subjected to the carbonyl addition to aldehyde promoted by Et2AlCl. Modest to good diastereoselectivity (50.0- 87.7%de) has been obtained by using (1R,2S,5R)-(-)-menthol as the chiral auxiliary (59.0-94.0% yield). The absolute configuration was unambiguously assigned by transforming the product to methyl (R)-α-methoxyphenylacetate.
Wei, Han-Xun,Willis, Steven,Li, Guigen
p. 8203 - 8206
(2007/10/03)
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