A rapid and efficient access to diaryldibenzo[b,f][1,5]diazocines.

2-Benzoylbenzoyl azides undergo facile cyclization under acidic conditions to give substituted dibenzo[b,f][1,5]-diazocines in good yields. This approach shortens the synthetic steps toward these compounds as compared with conventional methods. The mechanism of the diazocine synthesis is assumed to proceed by an unprecedented intermolecular [2 + 2] cyclization.