New strategies in using macromolecular catalysts in organic synthesis

Abstract

The use of soluble triphenylphosphine ligands to activate Pd(0) catalysts for allylic substitution of allyl esters or ethers by amines and stabilized carbanion nucleophiles and carboalkoxylation of aryl iodides and decar☐ylation of allylic β-keto esters is described. Pd(0) catalysts studied included Pd/C and dispersions of Pd(0) in an insoluble divinylbenzene crosslinked polystyrene resin. The effects of added triphenylphosphine on each reaction were seen in several ways. Small amounts of added phosphine increased the reaction rate 10-fold or more in most cases. Experiments to detect the nature of the active catalyst species and to differentiate between catalysis by a homogeneous species and catalysis by a heterogeneous species were performed. These experiments uniformly failed to demonstrate the presence of a homogeneous catalyst.