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

The inexpensive Keggin‐type polyoxometalate, i.e. H 3 PW 12 O 40 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 H 3 PW 12 O 40 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 (H 2 O/toluene, V/V = 1:5), and reused at least for four times without significant loss in activity.