One‐pot synthesis of trifluoromethylated benzimidazolines catalyzed by phosphotungstic acid with a low catalyst loading

The inexpensive Keggin‐type polyoxometalate, i.e. H3PW12O40 was found to be an effect catalyst for the condensation‐cyclization reaction of 1,2‐phenylenediamines and trifluoromethyl ketones to synthesize trifluoromethylated heterocycles, including benzimidazolines, benzoxazolines and benzothiazolines. Only 1 mol% of H3PW12O40 was required in this work, and the synergistic effect of proton and polyanion was vital for the reaction. Significantly, the POM catalyst could be easily recovered by using a biphasic solvent system (H2O/toluene, V/V = 1:5), and reused at least for four times without significant loss in activity.