Protonated bis-1, 2, 3-triazole as an anion-binding chiral brønsted acid for catalytic asymmetric friedel-crafts reaction of indoles with imines

The complex of chiral C2-symmetric bis-1, 2, 3-triazole and an achiral Brønsted acid is introduced as a new class of chiral acid catalysts. The catalytic activity and stereocontrolling ability of this chiral Brønsted acid can be tuned simply by changing the achiral acid. The synthetic relevance of this salient feature is demonstrated in the asymmetric FriedelCrafts reaction of indoles with N-sulfonyl imines.