Atypical Oxidation Reaction by Thionyl Chloride: Easy Two‐Step Synthesis of N‐Alkyl‐1,4‐dithiines

Abstract

Easy two‐step synthesis of a series of dithiines was performed from succinic anhydride via cyclization of the corresponding 4‐(alkylamino)‐4‐oxobutanoic acids (succinamic acids). The reaction, carried out in polar aprotic solvents, gave 4,8‐dithiine‐indacene‐1,3,5,7‐tetraones (diimides 3) via 3,7‐bis‐4,8‐dithia‐indacene‐1,5‐diones (diisoimides 2), which could be isolated. Surprisingly, in this reaction, thionyl chloride appeared as an oxidant, and this process seemed to be useful for the syntheses of S‐containing heterocyclic compounds such as 1,4‐dithiins. A mechanistic pathway was considered.

Keywords:

• Dithiine
• imide
• isoimide
• thionyl chloride

Acknowledgments

We gratefully acknowledge Dr. Masson and Dr. Gulea (Laboratoire de Chimie Moléculaire et Thio‐organique, Caen, France) for helpful discussions about the mechanistic pathway.