Dual ortho interaction in 2-substituted-3- (2-methylphenyl)-4(3H)-quinazolinones and their thio analogues under electron impact conditions

Article abstract of DOI:10.1002/jms.1190300206

Competing ortho interactions, involving the C=X and the ortho-methyl substituent on the 3-phenyl moiety, resulting in the eliminations of ^.CH₃ and ^.OH/^.SH from the molecular ions of 2-substituted-3-(2-methylphenyl)4(3H)-quinazolinones and their thio analogues, were observed, An intramolecular aromatic substitution of the heteroatom of C=X at the ortho-carbon of the 3-phenyl moiety ejecting the methyl group and a hydrogen transfer from the same ortho-methyl substituent to the heteroatom of C=X resulting in the expulsion of ^.XH are envisaged for the dual ortho interaction, Another expected fragmentation process Observed in these compounds is the transfer of the aryl group from the 3-position of the heterocycle to the heteroatom of C=X leading to the elimination of ArX^. from the molecular ions. The proposed fragmentation processes and the ion structures are supported by high-resolution data, B/E and B²/E linked-scan spectra, collisionally activated decomposition B/E spectra and deuterium isotopic labelling.