Mass spectral fragmentation of cis- and trans-1a,3-disubstituted 1, 1-dichloro-1a,2,3,4-tetrahydro-1H-azirino[1,2-a] [1, 5]benzodiazepines

Abstract

The mass spectrometric behaviour of six cis- and trans-1a, 3-disubstituted 1,1-dichloro-1a,2,3,4-tetrahydro-1H-azirino[1,2-a][1, 5]benzodiazepines has been studied with the aid of mass-analysed ion kinetic energy spectrometry and exact mass measurements under electron impact ionization. All compounds show a tendency to eliminate a neutral propene or styrene molecule from the diazepine ring and to simultaneously eliminate a chlorine atom from the aziridine ring to yield azirino[1,2-b][1,3]benzimidazole ions, and to lose hydrogen chloride plus propene or styrene to give quinoxaline ions. All compounds also show a tendency to eliminate N=CCl(2) or HN=CCl(2) to produce dihydro- or tetrahydroquinoline ions, and to eliminate sequentially hydrogen chloride and a chlorine atom to yield pyrrolo[1,2-a][1, 3]benzimidazole ions.