Acid-catalyzed rearrangement of diaryl hydrazides for the efficient synthesis of functionalized 2,2'-diamino-1,1'-biaryls

Diaryl hydrazides prepared from the Pd(0)- or Cu(I)-catalyzed coupling reactions of aryl hydrazides and aryl halides underwent the acid-catalyzed rearrangements to a series of previously unknown 2,2'-diaminobiaryls in good overall yields. The mildness of the reaction conditions allows the presence of various functional groups.