Cascade Synthesis of 4-Arylcoumarins: Pd-Catalyzed Arylations and Cyclizations with (E)-Ethyl 3-(2-Hydroxyaryl)acrylates and Triarylantimony Difluorides

摘要

Herein, we describe a simple general method for the synthesis of 4-arylcoumarins using pentavalent organoantimony compounds. The reactions of 3-(2-hydroxyaryl)acrylates with triarylantimony difluorides in the presence of Pd(OAc)(2) (10 mol-%) and 2,2'-bipyridyl (10 mol-%) at 80 degrees C under aerobic conditions afforded 4-arylcoumarins in good-to-excellent yields. This protocol involves a cascade oxidative Heck-type arylation followed by cyclization, with all the aryl groups in the triarylantimony difluoride transferred to the coupling products. Triarylantimony difluorides resulted in better outcomes than those obtained with other pentavalent organoantimony or bismuth compounds.