Iridium-catalyzed, intermolecular hydroamination of unactivated alkenes with indoles

Abstract

The addition of an N-H bond to an olefin is the most direct route for the synthesis of alkylamines. Currently, intermolecular hydroamination is limited to reactions of a narrow range of reagents containing N-H bonds or activated alkenes, and all the examples of additions to unactivated alkenes require large excesses of alkene. We report intermolecular hydroamination reactions of indoles with unactivated olefins. The reactions occur with as few as 1.5 equiv of olefin to form N-alkylindoles exclusively and in good yield. Characterizations of the catalyst resting state, kinetic data, labeling studies, and computational data imply that the addition occurs by olefin insertion into the Ir-N bond of an N-indolyl complex and that this insertion reaction is faster than insertion of olefin into the Ir-C bond of the isomeric C-2-indolyl complex.