NN-linked biazoles. Part 2. Attempted routes to the benzimidazol-1-yl radical. Synthesis of 2,2′-dimethyl-1,1′-bibenzimidazole

Abstract

A synthesis of a 1,1′-bibenzimidazole (2; R = Me), through two successive heterocyclizations on 2,2′-azoaniline, is reported. Alternative routes to (2) by direct formation of the N–N bond from the appropriate N-substituted-benzimidazoles were unsuccessful. The dimer (2) shows great thermal and photochemical stability towards hydrogen abstraction and addition to olefins. Although the N–N bond can be easily cleaved by irradiation in ethanol, all attempts to detect the neutral radical benzimidazol-1-yl (1; R = Me) from (2) have been unsuccessful. Hydrogen abstraction by (1) is, however, observed with 1-iodobenzimidazole as the precursor.