Synthesis and coordination chemistry of 4‐azabenzimidazole derivatives

AbstractA facile method for the preparation of N1‐ (1a–6a) and N3‐alkylated (1b–6b) 4‐azabenzimidazole derivatives is presented. Both isomers were obtained by alkylation of 4‐azabenzimidazole. The isomers were separated, and the preferred formation of the N1‐alkylated derivatives (1a–6a) was observed. The C2‐proton in the alkylated benzimidazoles can be exchanged for an iodine atom by treatment with methyl lithium and iodine, leading to N‐alkylated 2‐iodo‐4‐azabenzimidazoles 7a,b and 8a. 2,2′‐Bis(4‐azabenzimidazole) derivatives 9a,b and 10a were isolated as by‐products of the proton–halogen exchange. Treatment of the N1‐ or N3‐methyl‐4‐azabenzimidazoles 1a,b with methyl lithium and N‐chlorosuccinimide as a chlorine source proceeded to give 2‐chloro‐4‐azabenzimidazoles 11a,b without formation of the coupling products, but the yield of 2‐chloro‐1‐methyl‐4‐azabenzimidazole 11a is low (9%) whereas 2‐chloro‐3‐methyl‐4‐azabenzimidazole 11b has been obtained in reasonable yield (49%). The reaction of 3‐butyl‐2‐iodo‐4‐azabenzimidazole 7b with [IrCl2Cp*]2 gave the iridium complex 12, where 3‐butyl‐2‐iodo‐4‐azabenzimidazole is coordinating to the metal center via the N1 atom. The reaction of