Electron impact mass spectral fragmentation of 2a,4-disubstituted 2-chloro/2,2-dichloro-2,2a,3,4-tetrahydro-1H-azeto[2, 1-d][1,5]benzothiazepin-1-ones

The mass spectrometric behaviour of nine 2a,4-disubstituted 2-chloro/2,2-di chloro-2,2a,3,4-tetrahydro azeto[2,1-d][1,5]benzothiazepin-1-ones has been studied with the aid of mass-analysed ion kinetic energy, spectrometry and accurate mass measurements under electron impact ionization. All compounds show a tendency to eliminate a neutral chlorine atom, or a chloroketene, or neutral propene, or styrene or substituted styrene molecule, plus Cl and/o r H (or Cl) atom(s), to yield [M - Cl](+) ions, 2,3-dihydro-1,5-benzothiaze pine derivative ions, 4,5-dihydro-5H-1,5-benzothiazepin-4-one ions which ca n further lose CO to give 1,4-benzothiazine ions, Both molecular ions and [ M - Cl](+) ions show a tendency to eliminate an ethyl or benzyl/substituted benzyl radical to produce 2,2a-dihydro-1H-azeto[2,1-c][1,4]benzothiazin-1- one ions. The [M - Cl](+) ions could undergo rearrangement to yield 2,2a-di hydro-1H-azeto[2,1-d][1,5]benzothiaze-pin-1-one ions, 2,2a,3,4-tetrahydro-1 H-azeto[1,2-a]quinoline ions or 1,1a,2,3-tetrahydro-azirino[2,1-d][1,5]benz othiazepine ions by loss of an ethane or a benzene/substituted benzene, a S H radical or a CO molecule. The molecular ions could also undergo rearrange ment reactions to form other small fragment ions. Copyright (C) 2000 John W iley & Sons, Ltd.