Hydrogen-Borrowing Reduction/Dehydrogenative Aromatization of Nitroarenes through Visible-Light-Induced Energy Transfer: An Entry to Pyrimidoindazoles and Carbazoles.

Herein, we describe a novel visible-light-induced protocol for hydrogen-borrowing reduction/dehydrogenation aromatization/cyclization of nitroarenes by energy transfer. The present protocol does not require additional oxidants, hydrogen acceptors, and hydrogen evolution metal catalysts. The mechanistic studies demonstrated that the hydrogen-borrowing reduction/dehydrogenative aromatization process was initiated by the formation of active singlet species through efficient energy transfer of excited Ir[dF(CF 3 )ppy] 2 (dtbpy)PF 6 to nitroarenes.