Asymmetric Homoaldol Reactions of Metallated Dienyl Carbamates

Significance

Metallation of 1,3-dien-2-yl diisopropylcarbamates with BuLi in the presence of (-)-sparteine occurs in γ-position with high enantio­selectivity. The resulting lithium compounds react with electrophiles regio- and diastereoselectively. This reaction can be used in the enantioselective synthesis of a variety of polyfunctionalized alkenes. By using the single enantiomer of sparteine, both enantiomers of the desired products can be obtained by taking different regioisomers of the starting materials, changing the double bond geometry or by transmetallation of the lithium intermediates to the titanium species.