(Z)-Vinylcopper Species from 1,1-Dibromoalkenes and its Reactions

Significance

(Z)-Alkenylmetallic species are useful intermediates in organic synthesis, especially in the assembly of complex biologically active molecules. Whereas terminal (Z)-alkenylcuprates can be easily prepared by Normant carbocupration of acetylenes, the preparation of internal analogues is not that easy. The present method offers a good alternative to carbocupration in such cases. It is based on the stereoselective rearrangement of copper carbenoids. The resulting alkenylcopper species were found to easily add intramolecularly to Michael acceptors and open epoxides, giving cyclic adducts. In general, this is a useful synthetic protocol, which may find broad application, for instance, in the synthesis of terpenoids or similar molecules.