Amidation of Chloroalkenes Catalyzed by Tertiary Phosphine Complexes of Palladium(0)

Article abstract of DOI:10.1021/jo00232a038

Tertiary phosphine complexes of palladium(0) catalyze the amidation of vinyl chloride (VCl) with carbon monoxide and amines.The reaction is surprisingly fast and gives high yields of the Michael adduct derived from the amine with the corresponding acrylamide.The high rate with VCl is unusual among monochloroalkenes, being orders of magnitude greater than all three of the chloropropenes.The reaction is also stereospecific, with cis- and trans-1-chloropropene giving the propenamides with retention of configuration and no adduct formation.Basicity of the amine, coordination stereochemistry of the ligand, and the concentration of carbon monoxide and amine all influence the reaction rate in the ways that are sometimes unexpected, in both degree and direction.Like bromoalkenes and arenes, chloroalkenes undergo amidation through oxidative addition.This conclusion is based on the stereospecificity and the quantitative coupling of VCl to 1,3-butadiene when carbon monoxide is absent.Catalyst deactivation can occur and is mainly caused by the loss of ligand through conjugate addition with acrylamide.The rate of that reaction is controlled by the nucleophilicity of both the phosphine and the amine with which it competes.It is greatly suppressed in the presence of dimethylamine where amidation occurs with high catalyst turnover.