Electro-organic synthesis of isatins and hydrazones through C–N cross-coupling and C(sp²)–H/C(sp³)–H functionalization

An efficient and unique approach to synthesize isatin (indole-2,3-dione) from 2-aminoacetophenone under electrochemical conditions supported by I₂–DMSO through C–N cross-coupling and C(sp²)–H/C(sp³)–H functionalization is presented. This synthetic method spans a wide range of substituted 2-aminoacetophenone substrates. The use of iodine as a promoter and shorter reaction times produced good to very good yields of isatin derivatives, which is a significant improvement over the reaction in a batch process. Further, hydrazones of isatin were synthesized by using hydrazine hydrate which produces electrochemically active molecules, namely isatin-hydrazones. The hydrazones of acetophenone were also obtained using the same reaction protocol. Additionally, the effect of increasing scan rate studied using cyclic voltammetry shows that the process followed a diffusion-controlled mechanism.