Scalable Synthesis of Trifluoromethylated Imidazo-Fused N-Heterocycles Using TFAA and Trifluoroacetamide as CF3-Reagents

A scalable synthesis of trifluoromethylated imidazo-fused N-heterocyles from heterocyclic benzylamines using TFAA as trifluoromethylating reagent is presented. The reaction proceeds via intermediate benzylic N-trifluoroacetamides followed by dehydrative cyclization to the products. To further broaden the scope and practicality, a new method for the preparation of benzylic N-trifluoroacetamides via alkylation of trifluoroacetamide with benzyl (pseudo)halides was developed. Both methods proceed under mild conditions, and their symbiosis provides access to a wide range of novel CF3-heterocycles.