Synthesis of 3-substituted 2-trifluomethyl imidazo[1,2-a]pyridine through [3+2] cycloaddition of pyridinium ylide with trifluoroacetonitrile

A general approach to prepare 2-trifluoromethyl imidazo[1,2-a]pyridines by a [3+2] cycloaddition of pyridinium ylide with trifluoroacetonitrile is described. By using 2,2,2-trifluoroacetaldehyde O-(aryl)oxime as convenient precursor of trifluoroacetonitrile, the reaction exhibits a broad substrate scope of pyridinium ylides. The process is a scalable method for the synthesis of potentially bioactive class of 2-trifluoromethyl imidazo[1,2-a]pyridines.