Synthesis of Imidazoles from Ketimines Using Tosylmethyl Isocyanide (TosMIC) Catalyzed by Bismuth Triflate

The preparation of a series of 1,5-disubstituted-4-methyl imidazoles is reported, based on an unprecedented reaction between an acetimine and TosMIC in the presence of tert-butylamine and catalytic amounts of bismuth(III) triflate. The mechanism is believed to involve formation of an imidazoline intermediate, followed by the methyl group migration, and subsequent aromatization to the imidazole ring.