Synthesis of alicyclic esters via an intramolecular conjugate addition reaction. New method for generating (Z)-vinylcopper species from 1,1-dibromoalkenes

A novel cyclization reaction of a 1,1-dibromoalkene derivative having an α,β-unsaturated ester moiety was developed. Under the influence of Me₂CuLi, the 1,1-dibromoalkene was converted into a (Z)-vinylcopper species which in turn underwent an intramolecular conjugate addition reaction with the α,β-unsaturated ester moiety. Five-, six-, and seven-membered carbocycles were constructed by the present method. The substrate having an epoxide moiety also afforded a five-membered product via a 5-exo type intramolecular cyclization reaction.