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An Unprecedented Retro‐Mumm Rearrangement Revealed by ESI‐MS/MS, IRMPD Spectroscopy, and DFT Calculations
Author(s) -
Iacobucci Claudio,
Reale Samantha,
Aschi Massimiliano,
Oomens Jos,
Berden Giel,
De Angelis Francesco
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201800347
Subject(s) - infrared multiphoton dissociation , chemistry , dissociation (chemistry) , protonation , isomerization , tandem mass spectrometry , photochemistry , spectroscopy , rearrangement reaction , mass spectrometry , electrospray ionization , reaction intermediate , catalysis , ion , organic chemistry , physics , chromatography , quantum mechanics
Brønsted acids and protic solvents mediate acyl transfer, known as the Mumm rearrangement, from imidates to the corresponding acylamides. This represents a key step in several reactions, for example, the Ugi four‐component reaction (U‐4CR) and Passerini three‐component reaction (P‐3CR). Herein, an unprecedented break of the non‐reversibility of the Mumm rearrangement is reported. A combination of electrospray tandem mass spectrometry (ESI‐MS/MS), infrared multiphoton dissociation (IRMPD) ion spectroscopy and theoretical calculations demonstrates the occurrence of the retro‐Mumm rearrangement of protonated isopeptides in the gas phase. In the gas phase, the extra proton acquired during ESI promotes the backward isomerisation reaction in a catalytic fashion.