Synthesis of 2-(Trifluoromethyl)indoles via Domino Trifluoromethylation/Cyclization of 2-Alkynylanilines.

A new method for the synthesis of 2-(trifluoromethyl)indoles using easily accessible 2-alkynylanilines and a well-established fluoroform-derived CuCF3 reagent is described. This method utilizes a domino trifluoromethylation/cyclization strategy to construct the indole cores with no ambiguity of the CF3 position. The intriguing 3-formyl-2-(trifluoromethyl)indoles can also be synthesized by this protocol, which are useful intermediates for the preparation of trifluoromethylated drug analogues. The ultimate CF3 source is the inexpensive industrial byproduct fluoroform.