Cu(I)-Catalyzed Oxidative Cyclization of Alkynyl Oxiranes and Oxetanes

In the presence of a Cu(l) catalyst and a pyridine oxide, alkynyl oxiranes and oxetanes can be converted into functionalized five- or six-membered alpha,beta-unsaturated lactones or dihydrofuranaldehydes. This new oxidative cyclization is proposed to proceed via an unusual allenyloxypyridinium intermediate.