Synthesis of Benzo[ c ][2,7]naphthyridinones and Benzo[ c ][2,6]naphthyridinones via Ruthenium-Catalyzed [2+2+2] Cycloaddition between 1,7-Diynes and Cyanamides.

A convenient method for the ruthenium-catalyzed synthesis of benzo[ c ]naphthyridinone derivatives is reported. The [2+2+2] cycloaddition from various mono- and disubstituted 1,7-diynes and cyanamides provided benzo[ c ][2,7]naphthyridinones as major products and benzo[ c ][2,6]naphthyridinones as minor ones in yields of ≤79% and regioselectivities of ≤99:1. This method is amenable to internal and terminal diynes and a number of cyanamides with diverse functional group tolerance.