Highly Stereoselective Asymmetric Construction of an Acyclic Carbon Skeleton Having Two Adjacent Alkyl Substituents by Michael Addition of Optically Active Allenyltitaniums to Alkylidenemalonates

Abstract

[reaction: see text]. Enantio-enriched allenyltitaniums prepared in situ by the reaction of optically active secondary propargyl phosphates with a divalent titanium reagent Ti(O-i-Pr)4/2i-PrMgCl react readily with alkylidenemalonates with excellent regio- and diastereoselectivities to afford the Michael addition products with a high optical purity, thus opening up a new asymmetric method for construction of an acyclic carbon skeleton bearing two adjacent alkyl substituents.