Enantioselective addition of an alkyllithium compound across a double bond is achieved by the complexation of various primary or secondary organolithium compounds with (−)‐sparteine [Eq. (a)]. This synthetic route is effective, simple, and may be useful for the synthesis of chiral disubstituted cyclopropanes.

Carbometalation of a 1,Z-disubstituted olefin leads to the formation of a new organometallic species bearing two contigu-

No abstract

A stoichiometric or catalytic amount of (À)-sparteine can serve as a promoter for the enantioselective carbolithiation of cinnamyl derivatives by primary and secondary organolithium compounds. The enantiofacial choice of the addition reaction is dependent on the stereochemistry of the initial double bond. The resulting benzylic organolithium compounds can be derivatized to a linear phenylated chain that bears two contiguous stereogenic centers with given configurations. The use of the dimethyl acetal of the (E)-cinnamyl alcohol allows the highest enantioselective carbolithiation and by simply warming the reaction mixture to room temperature, the resulting benzylic organolithium intermediate undergoes a 1,3-elimination to give the chiral disubstituted cyclopropane in high enantiomeric excess (90 ± 95 % ee). Another significant finding is the observation that the Li ± Zn transmetalation in a benzylic species occurs with inversion of configuration, and the corresponding acyclic benzylic zinc halides have observable configurational stability at À 30 8C.