Mass spectrometer as a probe in the synthesis of 2-substituted-4(3H)- quinazolinones

The ortho interaction of the amide function with the N-aroyl group in 2- (substituted benzamido)benzamides 1-11 on electron impact leads to the elimination of H2O from the molecular ions, albeit a minor process, resulting in the formation of 2-substituted-4(3H)-quinazolinone radical cations. The mechanisms and ion-structure, proposed in the mass spectral study, are supported by high resolution data, Collision Activated Decomposition (CAD)-B/E-linked scan spectra and CAD MIKE spectrum. This mass spectrometry reaction has been fruitfully exploited in the laboratory to synthesise 4(3H)-quinazolinones 13-23 in excellent yields by the pyrolysis of 2-(substituted benzamido)benzamides.