A Ruthenium-Catalyzed Cyclization to Dihydrobenzo[ c ]phenanthridinone from 7-Azabenzonorbornadienes with Aryl Amides.

An efficient ruthenium(II)-catalyzed tandem C-C/C-N bond formation with aryl amides and 7-azabenzonorbornadienes has been developed to synthesize cis -fused dihydrobenzo[ c ]phenanthridinones. The amide group functions as a directing group as well as a leaving group and provides an easy access to the pharmaceutically useful benzo[ c ]phenanthridine alkaloids such as nitidine and fagaronine analogues. The present methodology is compatible with various functional groups with respect to azabicyclic alkenes and aromatic amides. The reaction mechanism involving directing-group-assisted C-H activation was proposed and supported by the deuterium labeling studies.