title: Heck-type coupling vs. conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyl compounds: a systematic investigation.
abstract: The competition between Heck-type coupling and conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls has been systematically investigated in a toluene-H(2)O biphasic system. Aside from the intrinsic nature of rhodium and the enolization of carbonyls, the phosphine supporting ligand on rhodium, the ratio of aryl boronic acid to alpha,beta-unsaturated carbonyl and the pH value of the aqueous phase were found to affect the competition significantly. Highly selective rhodium-based catalyst systems have therefore been developed for both Heck-type coupling and conjugate addition by synergistically tuning the supporting ligand, the boronic acid to olefin ratio and other reaction conditions. Conjugate addition with selectivity >99% and Heck-type coupling with selectivity of up to 100%, 98% and 84% for acrylates, acrylamides and methyl vinyl ketone, respectively, could be achieved in the rhodium-catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls using the corresponding optimized rhodium-based catalyst systems.
authors.affiliation: Laborotary of Advanced Materials and Department of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai, China200237. zougang@ecust.edu.cn
authors.forename: Gang
authors.initials: G
authors.lastname: Zou
authors.forename: Jianping
authors.initials: J
authors.lastname: Guo
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Wang
authors.forename: Wen
authors.initials: W
authors.lastname: Huang
authors.forename: Jie
authors.initials: J
authors.lastname: Tang