Photocatalytic One-Step Synthesis of Unsymmetrical Azines

Unsymmetrical azines are useful functional materials. The synthesis of unsymmetrical azines via iminyl radical N–N bond cross-coupling is dramatically challenging compared with the N–N homocoupling. The balance of two different iminyl radical intermediates is crucial. The control of the selectivity of N–N coupling over the N-abstraction of a hydrogen atom is also vital. A dual functional photocatalyst is the key to access the synergistic energy transfer (EnT)-single-electron transfer (SET) relay (EnT triggered SET) which can work both as an EnT PC and as a SET PC. In this work, by the strategy of synergistic EnT-SET relay catalyzed by the single dual functional organophotocatalyst CBZ6, the cross coupling of two different amyl iminyl radicals for the synthesis of unsymmetrical azines has been achieved. A twisted carbazole-cored highly electron-rich heterocycle CBZ6 plays dual roles as an EnT and SET organophotocatalyst.