ELECTRON-IMPACT MASS-SPECTRAL STUDY OF DIHYDROSPIRO-1,5-BENZODIAZEPINES

The mass spectrometric behaviour of some new 2,3-cycloalkano-3,4-dihydro-5H-7-benzoyl-1,5-benzodiazepine-4-spirocycloalkanes (1-4) and 2,4-diaryl derivatives (6-8) has been studied with the aid of metastable ions and high resolution data. In compounds 1-4, an extensive fragmentation of the cycloalkane ring with the losses of CnH2n+1 and CnH2n species from M+., followed by ring contraction leads to an abundant ion at m/z 236 for which a 2-methyl-7-benzoylbenzimidazole structure has been proposed. The structure of this ion has been studied by collision induced dissociation technique. The compounds 6-8 exhibit simple cleavages and ring contractions.