1 School of Petrochemical Engineering, Jiangsu Province Key Laboratory of Fine Petrochemical Engineering, Changzhou University, Changzhou 213164, P. R. China. jiangcheng@cczu.edu.cn.
DMSO and H2O is an efficient combination in the NH4OAc-promoted formylation of indole, where DMSO serves as a C1 carbon source. The mechanism study reveals that the procedure involves a usual and unusual Pummerer reaction.