Catalytic C6 Functionalization of 2,3-Disubstituted Indoles by Scandium Triflate

We report herein an unprecedented direct catalytic C6 functionalization reaction of 2,3-disubstituted indoles with various N-Ts aziridines catalyzed by Sc(OTf)(3) under mild conditions. Mechanistic studies revealed that a kinetically favored but reversible formal [3 + 2] annulation occurs initially. The direct C6 functionalization, although having a relatively higher energetic barrier, delivers the thermodynamically favorable products.