Solvent-Dependent Photocatalytic Acceptorless Dehydrogenation/Dehydrogenation-Coupling-Aromatization of N-Heterocycles

A solvent-dependent acceptorless dehydrogenation and dehydrogenation-coupling-aromatization of N-heterocycles at room temperature have been accomplished by using organophotoredox/cobalt dual catalysis. In the presence of acetone as solvent, the dehydrogenation product (heteroarenes) is obtained in good to high yields, whereas employment of DCE as solvent favors the formation of dehydrogenation-coupling-aromatization product (biheteroarenes). The photochemical reaction highlights noble metal-free, mild reaction conditions, atom economy, and chemo-selectivity. Primary mechanistic studies revealed a reductive quenching process was involved in the organo-photocatalytic cycle.