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Type: Artigo
Title: Charge Tags For Most Comprehensive Esi-ms Monitoring Of Morita-baylis-hillman (mbh)/aza-mbh Reactions: Solid Mechanistic View And The Dualistic Role Of The Charge Tagged Acrylate
Author: Galaverna
Renan; Camilo
Nilton S.; Godoi
Marla N.; Coelho
Fernando; Eberlin
Marcos N.
Abstract: Neutral and charge tagged reagents were used to investigate the mechanism of the classical Morita-Baylis-Hillman (MBH) reaction as well as its aza-version using mass spectrometry with electrospray ionization (ESI-MS). The use of an acrylate (activated alkene) with a methylimidazolium ion as a charge tag eliminates the requirement for adding acids as ESI(+) additives, which are normally used to favor protonation and therefore detection of reaction partners (reagents, intermediates, and products) by ESI(+)-MS. For both charge tagged reactions (MBH/aza-MBH), most reactants, intermediates, and the final adducts were efficiently detected in the form of abundant doubly and singly charged ions. Characterization of the reactions partners was performed-via both tandem mass spectrometry (ESI(+)-MS/MS) and accurate m/z measurements. The charge tagged reactions also showed faster conversion rates when compare to the neutral reaction, indicating a dualistic role for the charge tagged acrylate. It acts as both the reagent and a cocatalyst due to the inherent ionic-coordination nature of the methylimidazolium ion, which stabilizes the zwitterionic intermediates and reagents through different types of coordination ion pairs. Hemiacetal intermediates for the rate-limiting proton transfer step were also intercepted and characterized for both classical and aza-MBH charge tagged reactions.
Editor: Amer Chemical Soc
Citation: Journal Of Organic Chemistry. Amer Chemical Soc, v. 81, p. 1089 - 1098, 2016.
Rights: fechado
Identifier DOI: 10.1021/acs.joc.5b02651
Date Issue: 2016
Appears in Collections:Unicamp - Artigos e Outros Documentos

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