On the Superior Activity of In(I) versus In(III) Cations Toward ortho-C-Alkylation of Anilines and Intramolecular Hydroamination of Alkenes

An efficient ortho-C-alkylation of unprotected anilines with a variety of styrenes and alkenes using a univalent cationic indium­(I) catalyst is reported. Mechanistic studies revealed that the reaction likely proceeds via a tandem hydroamination/Hofmann–Martius rearrangement. The high compatibility between the cationic indium­(I) complex and primary anilines led us to develop an In­(I)+-catalyzed hydroamination of alkenes using unprotected primary and secondary alkenylamines. Computations support the catalytic activity of naked In­(I)+ ions, with an outer sphere mechanism for the C–N bond formation and a potentially inner sphere protodemetallation.