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 α-chloro-, bromo-, and iodo-enone olefins
can be synthesized with the kinetic E-geometry. Complementary
tetrasubstituted β-chloro-, 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.