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

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.