Mechanistic Insights into NN Bond Cleavage in Catalytic Guanylation Reactions between 1,2-Diarylhydrazines and Carbodiimides

Cleavage of the NN bond in 1,2-diarylhydrazine was achieved through an alkyllithium-catalyzed guanylation reaction of 1,2-diarylhydrazine with carbodiimide, affording guanidine and azo compounds. This NN bond cleavage via thermal rearrangement was driven by an intramolecular proton shift. No reductants, oxidants, bases, or external protons were needed. The proposed mechanism has been well elucidated by the isolation, characterization, and reaction studies of two important amido lithium intermediates and an ArHN-substituted guanidine.