A facile synthesis of benzo[c]phenanthridine alkaloids: oxynitidine and oxysanguinarine using lithiated toluamide–benzonitrile cycloaddition

Benzo[c]phenanthridine alkaloids oxynitidine and oxysanguinarine were synthesized from easily available starting benzonitrile 5 and toluamide 6 using toluamide–benzonitrile cycloaddition reaction in six steps. This method is so highly efficient that it could be a more useful way for preparing fully aromatized benzo[c]phenanthridine compounds.