Double annulation route to fused bicyclic compounds with three contiguous quaternary centers

Fused bicyclic and tricyclic compounds featuring two or three new C-C a bon ds, two new rings, two or three new stereocenters, and three new contiguous quaternary centers can be prepared stereoselectively, atom economically, a nd in one synthetic operation via a cascade reaction of two nonstereogenic, readily available starting materials: a tethered bis(malononitrile) and an internal alkynone. The course of the "double annulation" changes drastical ly with the structure of the starting materials, alternately affording tran s-decalins or cis-fused unsaturated lactones.