PTC based N-methylation of some imidazolyl non-fused biheterocycles

Abstract

The syntheses of 1,1'-dimethyl 2,2'-biimidazole (1), 1-methyl 2-(2'-pyridyl) benzimidazole (2) and 1,1'-dimethyl 2,2' bibenzimidazole (3) have been achieved by following a general PTC based methylation reaction of the corresponding unsubstituted analogues with dimethyl sulphate in presence of an intermediate lipophilic phase transfer catalyst, tetrabutyl ammonium bromide (TBAB). The method has been found to be superior to the earlier methods in terms of yield, simplicity, mild conditions and exclusive formation of N-methylated derivatives. The compounds have been characterised by UV, IR, H-1 & C-13 NMR and mass spectral studies.