A Mn(iii)-catalyzed arylboronic acid-based cascade reaction via a nonclassical organometallic-radical mechanism

Abstract

An efficient cascade reaction of arylboronic acids, o-cyanoaryl isocyanides, and indoles catalyzed by manganese(III) acetylacetonate which enables the construction of a series of 2-(1H-indol-3-yl)-2-phenylindolin-3-imines was developed. The transformation features high regioselectivity, broad substrate scope, and good functional group compatibility. Investigation of the reaction mechanism showed that instead of proceeding through a conventional radical pathway, the reaction possibly undergoes a nonclassical organometallic-radical route involving a sequence of transmetalation between arylboronic acid and Mn(acac)₃, insertion of isocyanide, intramolecular nucleophilic cyclization, and nucleophilic addition of indole.