The mass spectral fragmentation of 1a,3-disubstituted 4-benzoyl-1a,2,3,4- tetrahydrooxazirino[2,3-a][1,5]benzodiazepines

✍ Scribed by Jiaxi Xu; Liangbi Chen

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 52 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19991215)13:23<2424::aid-rcm786>3.0.co;2-y

✦ Synopsis

The mass spectrometric behaviour of four 1a,3-disubstituted 4-benzoyl-1a a][1,5]benzodiazepines has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization. All compounds show a tendency to eliminate a neutral oxygen atom, or oxygen atom plus benzoyl or aryl radicals, or oxygen atom plus CO molecule to yield 2,3-dihydro-1H-1,5-benzodiazepine derivative ions, or 1-benzoyl-2,3-dihydro-1H-1,5-benzodiazepine ions, which could further lose benzoyl to give 2,3-dihydro-1H-1,5-benzodiazepine ions. All compounds also show a tendency to eliminate a benzoyl radical to produce 1a,2,3,4-tetrahydrooxazirino[2,3-a][1,5]benzodiazepine ions. Both oxazirino[2,3-a][1,5]benzodiazepine ions and 2,3-dihydro-1H-1,5-benzodiazepine ions can undergo diazepine ring contraction rearrangement to yield benzimidazole ions by loss of propene or styrenes and other small fragments. The oxazirino[2,3-a][1,5]benzodiazepine ions [M -PhCO] also undergo rearrangement reactions to form benzoxazole ions and benzimidazole ions.