Dv. Ramana et Ms. Sudha, CLAISEN REARRANGEMENTS AND CYCLIZATIONS IN PHENYL PROPARGYL ETHERS UNDER ELECTRON-IMPACT CONDITIONS, Perkin transactions. 2, (4), 1993, pp. 675-678
An interesting Claisen rearrangement has been observed in phenyl propa
rgyl ether, yielding significant amounts of the [M - CO] ion under ele
ctron impact conditions. The other competing pathway is the loss of a
hydrogen radical from M.+ furnishing the most abundant ion in its mass
spectrum. Expulsion of a hydrogen radical from the propargylic carbon
leads to the propargylic cation species, while ejection of the ortho
hydrogen gives rise to a benzopyrylium cation structure. Substituents
on the phenyl ring do not favour the Claisen rearrangement, whereas ej
ection of the substituents producing benzopyrylium cations gains impor
tance. The mechanisms and ion structures proposed are supported by hig
h-resolution data, B/E and B2/E linked-scan spectra, Collision Activat
ed Decomposition (CAD)-B/E linked-scan spectra and deuterium isotope l
abelling.