Hydrodefluorination of N-acetylheptafluoro-2-naphthylamine by zinc in aqueous ammonia: synthetic outcomes and mechanistic considerations

Abstract

Dedicated to Professor Usein M Dzhemilev on the occasion of his 65th birthday AbstractReduction of the N-acetyl derivatives of heptafluoro-2-naphthylamine and its less fluorinated analogues by zinc in aqueous NH 3 has been investigated as a possible general and concise route to partially fluorinated N-(2-naphthyl)acetamides and, accordingly, 2-naphthylamines inaccessible by other ways. Quantum chemical calculations and CV measurement results have been used to discuss and justify the suggested reaction mechanism including two competing routes: fragmentation of a substrate radical anion and its complex with a zinc cation.

Structure and Stability of Pentafluoroaniline and 4-Aminononafluorobiphenyl Radical Anions: Optically Detected Electron Paramagnetic Resonance, Time-Resolved Fluorescence, Time-Resolved Magnetic Field Effect, and Quantum Chemical Study

“…The latter is typical of partially polyfluorinated arenes in general. Of late years, the convenient approach to these compounds was developed extensively based on the selective hydrodefluorination of polyfluoroarenes easily available by other methods. − Among these techniques, of special attention is the reduction by zinc in aqueous ammonia (the simplest reduction system hitherto used for this purpose), which is believed to occur through the formation of polyfluoroarene radical anions (RAs) , followed by their fragmentation with the elimination of fluoride anion. − Thus, the applicability of this system to synthesis is determined by its capability to reduce a polyfluoroarene, while the regioselectivity of the hydrodefluorination is determined by the fragmentation behavior of the respective RA, which justifies the interest to the structure and the properties of polyfluoroarene RAs.…”