Highly efficient Heck olefin arylation in the presence of iminophosphine-palladium(0) complexes

The Heck coupling of arylbromides with olefins such as styrene or butyl acrylate is efficiently catalysed by the iminophosphine-palladium(0) complex [Pd(dmfu)(P-N)] (dmfu=dimethyl fumarate; P-N=2-(PPh2)C6H4-1-CH=NC6H4OMe-4) (1) in polar solvents. With activated aryl bromides such as 4-bromoacetophenone turnover numbers of up to 20,000 can be achieved at 140 C in 2 h The presence of electron-donating groups leads to decreased reaction rates, nevertheless, high substrate conversions can be obtained in reasonable reaction time,,. Kinetic studies indicate that complex 1 is only a precursor of the actual catalytic species. Experiments aimed to demonstrate the intervention of metallic palladium did not lead to conclusive findings. (c) 2005 Elsevier B.V. All rights reserved.