DUAL ORTHO INTERACTION IN UBSTITUTED-3-(2-METHYLPHENYL)-4(3H)-QUINAZOLINONES AND THEIR THIO ANALOGS UNDER ELECTRON-IMPACT CONDITIONS

Competing ortho interactions, involving the C=X and the ortho-methyl s ubstituent on the 3-phenyl moiety, resulting in the eliminations of (C H3)-C-. and (OH)-O-./(SH)-S-. from the molecular ions of ubstituted-3- (2-methylphenyl)-4(3H)-quinazolinones and their thio analogues, were o bserved An intramolecular aromatic substitution of the heteroatom of C =X at the ortho-carbon of the 3-phenyl moiety ejecting the methyl grou p and a hydrogen transfer from the same ortho-methyl substituent to th e 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 th e 3-position of the heterocycle to the heteroatom of C=X leading to th e elimination of ArX(.) from the molecular ions, The proposed fragment ation processes and the ion structures are supported by high-resolutio n data, B/E and B-2/E linked-scan spectra, collisionally activated dec omposition B/E spectra and deuterium isotopic labelling.