The Claisen rearrangement of protonated allyl phenyl ether

Abstract

Molecular protonated ions of ally1 phenyl ether undergo a Claisen rearrangement both in the ion source and along the flight path. The rearranged ions undergo fragmentation, the predominant loss being ethene, and only a small contribution from loss of carbon monoxide is observed. Collision-indoced dissociation spectra are used to verify the structures of the daughter ions. These spectra, together with other evidence of an acid-induced ortho rearrangement, allow a mechanism to be proposed for the ethene loss. In contrast, molecular protonated ions of propargyl phenyl ether lose exclusively carbon monoxide.

Fragmentation pathways of selectively labeled propranolol using electrospray ionization on an ion trap mass spectrometer and comparison with ions formed by electron impact

“…These observations are consistent with m/z 183 arising from rearrangement through a six-membered transition state to add the three-carbon portion of the side-chain to the 2'-position on the naphthalene ring of the molecule, as e in Scheme 1. This rearrangement is similar to the Claisen rearrangements observed for phenyl allyl ether, phenyl allenyl ether and phenyl propargyl ether under positive CI 7 and EI 8,9 conditions. The retention of all five deuterium atoms in 2e rules out protonated naphthyl propargyl ether as a possible structure for e. Possible stepwise fragmentation pathways to e appear in Scheme 1.…”

Protonated nitro group as a gas-phase electrophile: Experimental and theoretical study of the cyclization of o-nitrodiphenyl ethers, amines, and sulfides

“…From P 12 , the OH radical loss would involve a simple homolytic bond cleavage, and the entropic factors in the transition states would be favorable to cleavage. 8 , respectively, to yield [M + H -H 2 O] + ions, P 2 and P 2c , respectively (Scheme 2c), the latter with reverse activation energy ≥ 300 kJ/mol (Scheme 3, Table 4b). The product [M + H -H 2 O] + ion, P 2c , is a substituted, protonated cyclic ketone, which can extrude CO to form the second-generation product ion, [M + H -(H 2 O + CO)] + , P 6 (Scheme 2c).…”

“…Fast atom bombardment (FAB), chemical ionization (CI) and electrospray ionization (ESI) readily generate protonated molecules or [M + H] + ions, and well established mass spectrometric methods for ion chemistry, reveal the properties of and the mechanisms for the reactions of protonated molecules in the absence of a solvent. The acid-catalyzed rearrangement of allyl phenyl ether, using chemical ionization (CI) mass spectrometry, is one example of the utility of mass spectrometry in this area [8]. A recent report by Cooks and coworkers [9] on the reduction of nitro aromatic compounds to arylnitrenium ions in the gasphase by radical cations of vinyl halides demonstrate that 'gas-phase synthetic chemistry' remains of current interest.…”

Gas Phase Decarbonylation and Cyclization Reactions of Protonated N-Methyl-N-Phenylmethacrylamide and Its Derivatives Via an Amide Claisen Rearrangement

“…Gas phase Claisen rearrangements of protonated allyl phenyl ethers [26], protonated Nallylaniline [27], and protonated benzyloxy indoles have been investigated by mass spectrometry [28]. Similar gas phase Claisen rearrangement reactions have been reported in the dissociation process of radical cations formed by electron ionization mass spectrometry (EI-MS) [29][30][31][32][33].…”