Mechanistic study of pyrazole synthesis via oxidation-induced N-N coupling of diazatitanacycles.

Metal-mediated inner-sphere N-N coupling is an uncommon route to N-N bond formation. Herein, we report a mechanistic study of pyrazole formation via oxidation-induced N-N coupling of diazatitanacycles. In TEMPO oxidation reactions, the first of two oxidations is rate limiting and TEMPO coordination to Ti is critical for reactivity. In oxidations with Fc + salts, coordinating counteranions such ( eg. Cl - ) aid an "inner-sphere-like" oxidation.