A Copper(I)-Catalyzed Addition/Annulation Sequence for the Two‑Component Synthesis of γ‑Ylidenebutenolides

A highly efficient Cu­(I)-catalyzed addition/annulation sequence has been developed for the synthesis of (Z)-ylidenebutenolides employing readily available α-ketoacids and alkynes as substrates. The reactions employ a simple commercially available Cu­(I)-catalyst, display good substrate scope, and deliver products with high stereoselectivity. The synthetic utility of the method is demonstrated by the straightforward derivatization of the ylidene­butenolides into a diverse range of heterocycles, and also by the preparation of the natural product bovolide, and analogs thereof.