Electron impact mass spectra of 1a,3-disubstituted 1,1-dichloro-1,1a, 2,3-tetrahydroazirino [2,1-d][1,5]benzothiazepines

Abstract

The mass spectrometric behaviour of eight 1a,3-disubstituted 1, 1-dichloro-1,1a,2,3-tetrahydroazirino[2,1-d][1,5]benzothiazepines has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and exact mass measurements under electron impact ionization. All compounds show a tendency to eliminate a chlorine radical from the aziridine ring and then eliminate a neutral propene or substituted/unsubstituted styrene from the thiazepine ring to yield 1,4-benzothiazine ions. They can also lose hydrogen chloride and a chlorine radical, or lose two chlorine atoms, to undergo a ring enlargement rearrangement to produce 1,6-benzothiazocine ions, which can further eliminate propyne or phenylacetylene, or small molecular fragments, to yield some abundant fragment ions.