rearrangements rearrangements O 0140 -049Acylthioketene-Thioacylketene-Thiet-2-one Rearrangements.-Flash vacuum thermolysis (FVT) of acylthioketene (I) and its anisyl analogue at different temperatures is studied by Ar matrix IR spectroscopy as well as tandem mass spectrometry. It is found that acylthioketenes like (II), generated by FVT, undergo a 1,3-shift of the aryl group to generate thioacylketenes which cyclize to thietones. The 1,3-shift is accelerated by an electron-donating substituent (-OMe) at the migrating phenyl group. Thietones undergo CO extrusion to give arylthioketenes like (III) and cycloreversion to COS and arylacetylene. -(AMMANN, JEFFREY R.; FLAMMANG, ROBERT; WONG, MING WAH;

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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.

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A real-time analysis of the flash-vacuum pyrolysis products of 1-acetylbenzotriazole (1) and I-benzoylbenzotriazole (2) was performed by tandem mass spectrometry. In the temperature range 50(MOO0C, these compounds lose nitrogen, yielding N-acetyl-and N-benzoylcyclopenta-2,4-dienylidenemethaneimines (10 and 17, respectively). At higher pyrolysis temperatures, 1 gives 2-methylbenzoxazole, cyanocyclopentadiene, methylcyanocyclopentadiene(s), benzonitrile and ketene, which were identified by collision-activated dissociation mass spectrometry. Lowtemperature infrared experiments confirmed the pyrolytic transformation l(2) -+ lO(17) at mediated temperatures.

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