Stereoselective Synthesis of Pyrans from Epoxyalkenes: Dual Catalysis with Palladium and Brønsted Acid

Abstract

We describe regio- and stereoselective cycloisomerizations of alcohols tethered to epoxyalkenes, to construct alkene-substituted pyrans. These transformations are best catalyzed by Pd(PPh₃)₄ in the presence of phosphite ligands, and with diphenylphosphinic acid as an essential Brønsted acid cocatalyst for activation of the epoxyalkene.