Benzyl anion transfer in the fragmentation of N-(phenylsulfonyl)-benzeneacetamides: a gas-phase intramolecular S_NAr reaction

Abstract

In this study, we report a gas-phase benzyl anion transfer via intramolecular aromatic nucleophilic substitution (SNAr) during the course of tandem mass spectrometry of deprotonated N-(phenylsulfonyl)-benzeneacetamide. Upon collisional activation, the formation of the initial ion/neutral complex ([C6H5CH2(-)/C6H5SO2NCO]), which was generated by heterolytic cleavage of the CH2-CO bond, is proposed as the key step. Subsequently, the anionic counterpart, benzyl anion, is transferred to conduct the intra-complex SNAr reaction. After losing neutral HNCO, the intermediate gives rise to product ion B at m/z 231, whose structure is confirmed by comparing the multistage spectra with those of deprotonated 2-benzylbenzenesulfinic acid and (benzylsulfonyl)benzene. In addition, intra-complex proton transfer is also observed within the complex [C6H5CH2(-)/C6H5SO2NCO] to generate product ion C at m/z 182. The INC-mediated mechanism was corroborated by theoretical calculations, isotope experiments, breakdown curve, substituent experiments, etc. This work may provide further understanding of the physicochemical properties of the gaseous benzyl anion.

A comprehensive study on rearrangement reactions in collision‐induced dissociation mass spectrometric fragmentation of protonated diphenyl and phenyl pyridyl ethers

“…These rearrangement reactions pose problems in fragmentation pattern based structural elucidation. There have been several reports in the literature on organic rearrangement reactions such as the benzyl cation transfer, benzyl anion transfer, proton transfer, sulfonyl transfer, and elimination reactions, etc., during the fragmentation process. Thus, it is necessary to understand clearly the fragmentation pathways of compounds to overcome the challenges in structural elucidation.…”