Vanadium-Catalyzed Synthesis of Geometrically Defined Acyclic Tri- and Tetrasubstituted Olefins from Propargyl Alcohols

A highly selective formation of geometrically defined acyclic tri- and tetrasubstituted alkenes from inexpensive and readily available propargyl alcohols is described. Through vanadium oxo catalysis, tri- and tetrasubstituted alpha-chloro-, bromo-, and iodo-enone olefins can be synthesized with the kinetic E-geometry. Complementary tetrasubstituted bromo-, and iodo-enone olefins with Z-geometry can be accessed through a metal free 1,2-aryl shift. The utility of these geometrically defined vinyl halides is demonstrated through cross-coupling reactions to form all-carbon tetrasubstituted olefins with near complete retention of starting olefin geometry as well as through the total synthesis of (+/-)-myodesmone.