Copper-Catalyzed Decarboxylation of Α,Β-Unsaturated Carboxylic Acids with N-Fluorobenzenesulfonimide: Synthesis of Enamines

A highly efficient and easy protocol Copper-catalyzed decarboxylative amination of α,β-unsaturated carboxylic acids with N-Fluorobenzenesulfonimide as a nitrogen source and an oxidant has been developed. The present protocol, which includes C-N bond formation in one step through addition, oxidation, and decarboxylation processes, leads to the desired enamine products. Thus the results of the experiments have shown that this study is the novel example of copper-catalyzed decarboxylative atom transfer radical of α,β-unsaturated carboxylic acids. In addition, a wide range of enamines with different substitution patterns was prepared and different groups such as chloro, Bromo, fluoro, methyl, and methoxy were employed to give products in moderate to excellent yield. The mechanistic investigations revealed that the catalytic cycle was initiated by the oxidation of Cu (I) with NFSI to provide the nitrogen-centered radical species. Finally, all the products were characterized by 1H NMR, 13C NMR, and HRMS spectra.