General Construction of Thioamides under Mild Conditions: A Stepwise Proton Transfer Process Mediated by EDTA

Abstract A general and clean method for the one‐pot synthesis of thioamides was investigated using a combination of experiments and quantum chemical calculations. Ester, amide, and elemental sulfur were employed as starting materials and ethylene diamine tetraacetic acid (EDTA) as catalyst. Both alkyl and aryl thioamides with various functional groups were obtained in moderate to good yields. Neither transition metals nor external oxidants were required in this reaction. The catalytic performance of EDTA originates from a stepwise, proton transfer process in which EDTA transports a proton from the benzyl carbon to a sulfur atom. Such a process is concerted by discrete charge transfer such that the associated barrier gets lowered.