A Novel Copper Chelate Catalyzed Ring Closure Reaction of 1,2-Bisketenes with Alcohols To Give 5-Alkoxy-2,3-dihydrofuran-2-ones.

Copper complexes with distorted tetrahedral structure in solution catalyze regioselectively the cyclization of 1,2-bisketenes with alcohols to give 5-alkoxy-2,3-dihydrofuran-2-ones in very high yields (shown on the right). It seems remarkable that these new compounds could remain undiscovered despite having structural similarities with a great number of well-investigated and biologically active butenolides.