Reaction of electrogenerated cyanomethyl anion with cyclohexylisocyanate: synthesis of N-(cyclohexylcarbamoyl) acetamide. An unexpected product

The cyanomethyl anion, generated by cathodic reduction of a solution of ACN-TEABF4 , is a bidentate species. The negative charge is delocalized alternatively on the nitrogen atom and on the methylene carbon, but the literature reports a computational study, where the maximum electron density results on the carbon atom. Hence, methylene carbon is the nucleophilic site [1]. The contamination with water of the cathodic solution gave us the opportunity to investigate alkyl isocyanate reactivity toward electrogenerated anions. The cathodic reduction of a ACN- TEABF4 solution led to the formation of both hydroxide and cyanomethyl anions. The reaction of the catholyte with cyclohexylisocyanate led to the exclusive formation of acetamidated product, with no traces of cyanomethylated one. On the contrary, when reacting with benzaldehyde only the cyanomethylated was isolated [2]. Several experiments were carried out to understand the unexpected behavior of cyclohexylisocyanate. The examined variables were the amount of charge given during electrolysis and the possible rearrangement of the cyanomethylation product. Moreover, computational analysis allowed to state the higher stability of acetamidated product with respect to the cyanomethylated one. References [1] Rossi et al. J. Org. Chem. 1976, 41, 3367 [2] Scarano et al. J. Electrochem. Soc. 2020, 167, 155514