Electron impact mass spectral fragmentation of 3a,5-disubstituted 1,3-diphenyl-3a,4,5,6-tetra-hydro-3H-1,2,4-triazolo[4,3-a][1,5]benzo-diazepines

✍ Scribed by Jiaxi Xu; Qihan Zhang; Chenbo Wang

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 66 KB
• Volume: 14
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/1097-0231(20001230)14:24<2339::aid-rcm170>3.0.co;2-l

✦ Synopsis

The mass spectrometric behaviour of six 3a,5-disubstituted 1,3-diphenyl-3a,4,5,6-tetrahydro-3H-1,2,4triazolo[4,3-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 (substituted) styrene molecules, aryl radicals, arylmethyl radicals or phenylnitrene (PhN:). All of the resulting fragment ions, except [M À PhN:] Á , could further undergo a reverse [2 3] cycloaddition. The [M À PhN:] Á ions could further lose styrene derivatives and undergo a ring enlargement rearrangement. The molecular ions also show a tendency to eliminate a phenyl radical, and the [M À Ph] ions could eliminate styrene derivatives. The [M À R 1 CH = CH 2 ] Á ions could further lose NH 2 to yield stable tetracyclic 1,3-diphenyl-1,2,4-triazolo[4,3-d]phenanthridine ions, which could further lose benzonitrile, or undergo a reverse [2 3] cycloaddition. The molecular ions could also undergo a reverse [2 3] cycloaddition to produce N-phenylbenzonitrile imine ions and 2,4-disubstituted 2,3-dihydro-1H-1,5benzodiazepine ions, whose further fragmentations were also investigated.