Electron impact mass spectral fragmentation patterns of 2a,4-disubstituted5-benzoyl-2-chloro-2a,3,4,5-tetrahydroazeto[1,2-a][1,5]-benzodiazepin-1(2H)-ones

The mass spectrometric behaviour of six 2a,4-disubstituted 5-benzoyl-2-chlo ro-2a,3,4,5-tetrahydroazeto[1,2-a][1,5]benzodiazepin-1(2H)-ones has been st udied with the aid of mass-analysed ion kinetic energy spectrometry and acc urate mass measurements under electron impact ionization, All compounds sho w a tendency to eliminate a chlorine atom, a chlorine atom plus benzaldehyd e, benzoyl radical, chloroketene or chlorine atom plus CO and H2O molecules to yield, respectively, [M - Cl](+) ions, 2a,4-disubstituted 2a,3-dihydroa zeto[1,2 -a][1,5]benzodiazepin-1(2H)-one ions, [M - PhCO](+) ions, 2,4-disu bstituted 1-benzoyl-2,3-dihydro-1H-1,5-benzodiazepine ions, or 1,2,4-trisub stituted 1H-1,7-benzodiazonine ions, which could also be formed from [M - C l](+) ions by loss of CO and H2O molecules simultaneously, The [M - Cl](+) ions could further lose benzoyl radical to form [M - Cl - PhCO](+) ions, or lose benzoyl amide and undergo a rearrangement to form 4,6-disubstituted 1 -benzoazocine-2(1H)-one ions. The [M - PhCO](+) ions could eliminate NH to produce 2a,4-disubstituted 2,2a,3,4-tetrahydroazeto[1,2,-a]quinolin-1-one i ons, which could further eliminate chloroketene, CO and/or HCl to produce s ome important ions, respectively. 2,4-Disubstituted 1-benzoyl-2,3-dihydro-1 H-1,5-benzodiazepine ions could lose benzoyl radical to yield 2,4-disubstit uted 2,3-dihydro-1H-1,5-benzodiazepine ions, which could further yield othe r small fragment ions by loss of propene/styrene or small fragments. Copyri ght (C) 2000 John Wiley & Sons, Ltd.