3,4-Annulated Indoles via Tandem Cyclopropane Ring-Opening/Conia-ene and Michael Addition/Conia-ene Reactions.

4-Alkynyl indoles, when treated with a benzylidene malonate or a donor-acceptor cyclopropane in the presence of a zinc halide, furnished 3,4-hexannylated or 3,4-heptannulated products, respectively, in fair to excellent yields. The reaction proceeds via a tandem addition/Conia-ene cyclization.