Formal [4 + 1]- and [5 + 1]-annulation by an S(N)2-conjugate addition sequence: stereoselective synthesis of highly substituted carbocycles.

K(2)CO(3)-mediated reactions of 6-bromo-2-hexenoates and 7-bromo-2-heptenoate with active methylene compounds deliver highly substituted cyclopentane and cyclohexane derivatives, respectively via a sequence of S(N)2-conjugate addition reactions (formal [4 + 1]- and [5 + 1]-annulation) in a diastereoselective manner.