Synthesis of 4-Ynamides and Cyclization by the Vilsmeier Reagent to Dihydrofuran-2(3H)-ones.

The room-temperature nucleophilic addition of vinyl azides to propargylic alcohols under BF3·Et2O catalysis provides an efficient synthesis of 4-ynamides. The procedure is operationally convenient, shows broad substrate scope, and is viable for the synthesis of multifunctional 4-ynamides. Further, a Vilsmeier intramolecular cyclization of 4-ynamides into dihydrofuran-2(3H)-ones has also been discovered, which represents the first report of alkynes being used as the nucleophiles in Vilsmeier-type reactions.