Highly stereoselective asymmetric construction of an acyclic carbon skeleton having two adjacent alkyl substituents by Michael addition of optically active allenyltitaniums to alkylidenemalonates

[GRAPHICS] Enantio-enriched allenyltitaniums prepared in situ by the reaction of optic ally active secondary propargyl phosphates with a divalent titanium reagent Ti(O-i-Pr)(4)/2i-PrMgCl react readily with alkylidenemalonates with excell ent regio- and diastereoselectivities to afford the Michael addition produc ts with a high optical purity, thus opening up a new asymmetric method for construction of an acyclic carbon skeleton bearing two adjacent alkyl subst ituents.