Functionalized 2,3′-Bipyrroles and Pyrrolo1,2-cimidazoles from Acylethynylpyrroles and Tosylmethylisocyanide

An efficient method for the synthesis of pharmaceutically prospective but still rare functionalized 2,3′-bipyrroles (in up to 80% yield) by the cycloaddition of easily available acylethynylpyrroles with tosylmethylisocyanide (TosMIC) has been developed. The reaction proceeds under reflux (1 h) in the KOH/THF system. In the t-BuONa/THF system, TosMIC acts in two directions: along with 2,3′-bipyrroles, the unexpected formation of pyrrolo1,2-cimidazoles is also observed (products ratio~1:1).