Borate Esters as Alternative Acid Promoters in the Palladium-Catalyzed Methoxycarbonylation of Ethylene

摘要

Since the early 1990s there has been considerable interest in the alkoxycarbonylation of olefins, a potentially important reaction for the production of commodity chemicals. The attention devoted to this chemistry resulted in the development by Lucite International of a two-step process for the production of methyl methacrylate (MMA) in which the initial step, the carbonylation of ethylene, is catalyzed by a palladium/bidentate phosphine/acid system. The choice of acid in this step is important, as it determines the type of counterion available for the cationic palladium species. A strongly coordinating anion will reduce the rate of the kinetically important addition of CO to C2H4, whereas weakly coordinating or noncoordinating anions allow the facile coordination of these reagents.