Copper(ii)-catalyzed coupling reaction: an efficient and regioselective approach to N′,N′-diaryl acylhydrazines

Using N'-aryl acylhydrazines as aryl donors, a novel copper(ii)-catalyzed homo-coupling reaction of N'-aryl acylhydrazines has been developed for the synthesis of N',N'-diaryl acylhydrazines. We also provided a complementary procedure for the preparation of unsymmetrical diaryl acylhydrazines via cross-coupling reaction. These protocols featured mild reaction conditions, wide functional group tolerance and highly regioselective products. Control experiments indicated that this kind of coupling reaction might undergo a transient acyl diazene intermediate.