Dioxygen-promoted regioselective oxidative Heck arylations of electron-rich olefins with arylboronic acids

作者：Andappan MMS; Nilsson P; von Schenck H; Larhed M^*

来源：Journal of Organic Chemistry, 2004, 69(16): 5212-5218.

DOI：10.1021/jo049434t

Arylations of electron-rich heteroatom-substituted olefins were performed with arylboronic acids. This appears to constitute the first example of palladium(II)-catalyzed internal Heck arylations. The novel protocol exploits oxygen gas for environmentally benign reoxidation and a stable 1,10-phenanthroline bidentate ligand to promote the palladium(II) regeneration and to control the regioselectivity. Internal arylation is strongly favored with electron-rich arylboronic acids. DFT calculations support a charge-driven selectivity rationale, where phenyls substituted with electron-donating groups prefer the electron-poor alpha-carbon of the olefin. Experiments, verified by calculations, confirm the cationic nature of the catalytic route. This Heck methodology provides a facile and mild access to functionalized enamides. Controlled microwave heating and increased oxygen pressure were used to further reduce the reaction time to 1 h.

• 出版日期2004-8-6