ChemInform Abstract: Chemical and Spectroscopical Evidence for an Electron‐Transfer Mechanism in the Reaction of Arenesulfonyl Chlorides with Anions

Abstract

The reaction of amide and amidate anions 2 with ptoluenesulfonyl chloride (1) under Merent reaction conditions gives rise to the total or prrrtial reduction of the acyl halide to p-toluenesulfiaic acid (5) and acylatioo compounds in variable amounts depending on the crowding at the anionic center. This indicates that a SingIe-Electron Transfer (SET) mechanism is involved in the reactions of 1 with anions. Unpaired electron species are detected by RTR in the course of the reactions.It is well-established that sulfur-substituted aromatic rings such as aryl sulfones 'I, arenesulfonates 21, or arenesulfonamides 3, are able to accept one electron under thermal or photochemical conditions when allowed to react with anions or other chemical and electrochemical electron sources. By contrast, the behavior of arenesulfonyl chlorides as single-electron acceptors, in spite of their extended use in organic synthesis, has not been investigated so far although they should be expected to accept a single electron from anions as efficiently or even more than the above mentioned sulfurcontaining groups. Arenesulfonyl chlorides are reduced by usual reductors (hydride or sullite anions) with great ease and also by anions such as acetylide, enolate, sulfide, mercaptide, thiosulfate, cyanide, dithionite, arsenite, iodide, and dithi~carbonate~' in reactions that have not been investigated in depth from a mechanistic point of view.For these reasons, we decided to investigate the reactivity of ptoluenesulfonyl chloride (1) with nucleophiles NueM@ (2) such as amide and amidate anions, species that might behave alternatively as two-electron or single-electron donors6'.The reaction of nucleophiles 2 with p-toluenesulfonyl chloride under different reaction conditions gave rise to total or partial re-Scheme 1 ~-C H~C~H~S O~C I