Abstract: The electron impact time-of-flight(TOF) mass spectra of the title compounds were studied to establish their fragmentation processes. With the high resolution of the TOF instrument, the exact mass for each fragment was determined. These data were used to infer the molecular formulas and the elemental compositions for all the molecular ions and fragments through software interpretation. By further applying the fragmentation regularity, the majority of ions were fully assigned. The main fragmentation pathways of the title compounds include the formation of molecular ions by the loss of R¹ groups in the 4-position and the ester groups in the 5-position. The formed ion can be further fragmented by the elimination of MeOH.

Key words: 3,4-Dihydropyrimidinone, Time-of-flight mass spectrometry, Electron impact