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.