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Gas-Phase Smiles Rearrangement of ortho-Nitro-substituted Diaryliodonium Cations and Their Mechanistic Insights
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  • Haoyang Wang,
  • Wu-Zhi Wei,
  • Cheng Pan,
  • Ling Lin,
  • Jianwei Han
Haoyang Wang
Chinese Academy of Sciences Shanghai Institute of Organic Chemistry

Corresponding Author:[email protected]

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Wu-Zhi Wei
University of Shanghai for Science and Technology
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Cheng Pan
East China University of Science and Technology
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Ling Lin
Chinese Academy of Sciences Shanghai Institute of Organic Chemistry
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Jianwei Han
East China University of Science and Technology
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Rationale: Diaryliodonium salts are useful electrophilic reagents in organic chemistry, finding extensive applications in arylations and photo-induced polymerizations. However, the comprehensive mechanistic investigations, particularly concerning the mass spectrometric behaviors of diaryliodonium salts, are relatively scarce in the literatures. Methods: Diaryliodonium salts could be readily ionized in ESI-MS to give [Ar 1-I +-Ar 2], and the high-resolution ESI-MS/MS experiments were conducted to investigate their gas-phase chemical reactions. Results: Investigations on ESI-MS/MS of [Ar 1-I +-Ar 2] revealed two major fragmentation patterns: 1) Reductive elimination resulting the diaryl coupling product ion [Ar 1-Ar 2] +• by the loss of I. 2) Generating aryl cations [Ar 1] + or [Ar 2] + through cleavage of the C–I bonds. We unrevealed that the introduction of NO 2 into Ar 2 of [Ar 1-I +-Ar 2] could lead to an unexpected fragmentation ion [Ar 1O] + in MS/MS, arising from an O-atom transfer process from NO 2 to Ar 1. Particularly, when NO 2 was ortho-positioned to the iodine in Ar 2, the [Ar 1O] + sometimes exhibited dominant behavior. Conclusions: Comprehensive ESI-MS/MS studies and theoretical calculations provided strong support for the O-atom transfer mechanistic pathway: [Ar 1-I +-( o-NO 2-Ar 2)] initially underwent a Smiles rearrangement to the intermediate [Ar 1-O-( o-NO-Ar 2I)] +, which subsequently dissociated to [Ar 1O] + or [ o-NO-Ar 2I] +•. Herein, we proposed an unexpected ” ortho-effect” in the gas-phase fragmentation reaction of [Ar 1-I +-( o-NO 2-Ar 2)], in which the crucial determinant factor for the aryl migration was identified as the Smiles rearrangement reaction.
17 Nov 2023Submitted to Rapid Communications in Mass Spectrometry
17 Nov 2023Assigned to Editor
17 Nov 2023Submission Checks Completed
17 Nov 2023Review(s) Completed, Editorial Evaluation Pending
20 Nov 2023Reviewer(s) Assigned