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

Abstract

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.