REGIOSELECTIVE AND STEREOSELECTIVE ALLYLATION OF ORGANOMETALLIC REAGENTS

Regio- and stereoselective allylation reactions of organocopper and organozinc reagents have been developed, investigated by NMR for the reagent composition, and examined for their synthetic potential with respect to 1,2-asymmetric induction. The S(N)2'-selective reaction of organocopper and organozinc reagents with allylic chlorides having a chiral center at the delta-position proceeds with up to 100% diastereoselectivity. The observed 1,2-asymmetric induction conforms to pure steric control (Cram-Felkin-Anh model) even in cases where conventional chelation control may seem to operate, and the level of the selectivity was found to be much higher than those found for the additions of organometallics to structurally comparable alpha-substituted carbonyl compounds. Some examples of 1,4-asymmetric induction are also described.