Synthesis of Indolo[1,2-a][1,8]naphthyridines by Rhodium(III)-Catalyzed Dehydrogenative Coupling via Rollover Cyclometalation.

The rhodium-catalyzed dehydrogenative coupling of N-pyridylindoles with alkynes proceeds smoothly through rollover cyclometalation to produce indolo[1,2-a][1,8]naphthyridine derivatives. A number of tetra-, penta-, and hexacyclic N-containing heteroaromatics can also be readily constructed in a similar manner. The L-shaped π-conjugated molecules exhibit intense solid-state fluorescence.