The Heck reaction: mechanistic insights and novel ligands

The kinetics of the Heck reaction of aryl iodides with methyl acrylate using phosphane ligands were studied. Triphenylphosphane strongly inhibited the reaction when used in excess over the Pd(0) precatalyst. The rate of reaction was found to be weakly dependent on the concentrations of both the aryl iodide and the alkene. The results indicate that the migratory insertion step is turnover limiting, with the oxidative addition to the aryl iodide being faster but not negligible. Phosphane sulfane hemilabile ligands were found to give good yields and good catalyst stability in Heck reactions. (C) 2000 Elsevier Science Ltd All rights reserved.