Claisen rearrangement of allyl phenyl ether and its sulfur and selenium analogues on electron impact

The electron impact (EI) mass spectrum of allyl phenyl ether (1) includes a n ion at m/z 106 that is formed mainly by the loss of CO from the molecular ion, as supported by high resolution and MS/MS data. The formation of the [M - CO](+) ion from 1 can be explained in terms of the Claisen rearrangeme nt of 1 after ionization in the ion source of the mass spectrometer, Simila rly, allyl phenyl sulfide (2) and allyl phenyl selenide (3) showed characte ristic ions corresponding to [M - CH3](+), [M - XH](+) (X = S or Se) and [M - C2H4](+.), and the formation of these ions are explained via Claisen rea rrangement of 2 and 3 in the ion source of the mass spectrometer resulting in a mixture of rearrangement products. The formation of molecular ions of 2-allyl thiophenol and 2-allyl selenophenol as intermediates, that cannot b e isolated as the neutrals from the solution phase Claisen rearrangement of 2 and 3, respectively, is clearly indicated in the gas phase. The mass spe ctra of the rearrangement products obtained from the solution phase reactio n were also consistent with the proposal of formation of these products in the ion source of the mass spectrometer. The formation of characteristic fr agment ions attributed to the Claisen rearrangement products are also evide nt in the collision induced dissociation spectra of the corresponding molec ular ions. Copyright (C) 2000 John Wiley & Sons, Ltd.