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Type: Artigo
Title: Exploring the intrinsic polar [4 + 2+] cycloaddition reactivity of gaseous carbosulfonium and carboxonium ions
Author: Basher, Muftah M.
Corilo, Yuri E.
Sparrapan, Regina
Benassi, Mario
Augusti, Rodinei
Eberlin, Marcos N.
Riveros, José M.
Abstract: as‐phase reactions of model carbosulfonium ions (CH3‐S+ = CH2; CH3CH2‐S+ = CH2 and Ph‐S+ = CH2) and an O‐analogue carboxonium ion (CH3‐O+ = CH2) with acyclic (isoprene, 1,3‐butadiene, methyl vinyl ketone) and cyclic (1,3‐cyclohexadiene, thiophene, furan) conjugated dienes were systematically investigated by pentaquadrupole mass spectrometry. As corroborated by B3LYP/6‐311 G(d,p) calculations, the carbosulfonium ions first react at large extents with the dienes forming adducts via simple addition. The nascent adducts, depending on their stability and internal energy, react further via two competitive channels: (1) in reactions with acyclic dienes via cyclization that yields formally [4 + 2+] cycloadducts, or (2) in reactions with the cyclic dienes via dissociation by HSR loss that yields methylenation (net CH+ transfer) products. In great contrast to its S‐analogues, CH3‐O+ = CH2 (as well as C2H5‐O+ = CH2 and Ph‐O+ = CH2 in reactions with isoprene) forms little or no adduct and proton transfer is the dominant reaction channel. Isomerization to more acidic protonated aldehydes in the course of reaction seems to be the most plausible cause of the contrasting reactivity of carboxonium ions. The CH2 = CH‐O+ = CH2 ion forms an abundant [4 + 2+] cycloadduct with isoprene, but similar to the behavior of such α,β‐unsaturated carboxonium ions in solution, seems to occur across the C = C bond
Subject: Íons
Espectrometria de massa
Country: Reino Unido
Editor: John Wiley & Sons
Rights: Fechado
Identifier DOI: 10.1002/jms.3109
Date Issue: 2012
Appears in Collections:IQ - Artigos e Outros Documentos

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