Synthesis of Novel Pyridobenzimidazoles Bonded to Indoleorbenzo[b]thio-phenestructures

Pyridobenzimidazoles 6a-iwere synthesized in very good to excellent yields (81-96%) by the condensation of substituted N-phenyl-o-phenylenediamines 4a-d with indole/benzo[b]thiophene-3-aldehydes 5a-t inmethoxyethanol under reflux conditions.The diamines 4a-d were prepared byfirst treating 2-chloro-3-nitropyridine (1)with suitably substituted anilines 2a-d then reducing the resulting3-nitro-N-phenylpyridin-2-amines 3a-d with tin(II)chloride using microwave heating in each case.