Highly stereoselective asymmetric construction of an acyclic carbon skeleton having two adjacent alkyl substituents by Michael addition of optically active allenyltitaniums to alkylidenemalonates.
[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.
Song
Y
Y
Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho Midori-ku, Yokohama, Kanagawa 226-8501, Japan.
Okamoto
S
S
Sato
F
F