Stereochemical effects in the EI mass spectra of cis- and trans-fused hexahydro-3,l-benzoxazines and –benzothiazines

Abstract

Dedicated to Professor Nikolai Zefirov on the occasion of his 70th birthday (received 05 Oct 04; accepted 20 Dec 04; published on the web 01 Jan 05) AbstractThe electron ionization mass spectra of cis-and trans-fused 2-oxo-(1,2), and 2-thioxo-4-phenyloctahydro-2H-3,l-benzoxazines (3,4), 2,4-diphenylhexahydro-3,1-benzoxazines (5,6) and 2-phenylimino-4-phenylhexahydro-3,l-benzoxazines (7,8) and -benzothiazines (9,10) were recorded, and the fragmentation pathways established and compared to their 4-unsubstituted counterparts. Effects of stereochemistry, substitution, and (in the case of 2-phenylimino derivatives) of an intramolecular cyclization of the [M-H] + ions were observed in the mass spectra. In general, mass spectral behavior was similar for the isomeric compounds although they could usually be differentiated from each other based on the relative abundances of their characteristic fragment ions.