Rm. Alvarez et al., Benzylic cleavage and McLafferty rearrangement under electron ionization conditions in the fragmentation of 5,6-dialkyl-2,4-diarylpyrimidines, RAP C MASS, 13(24), 1999, pp. 2480-2488
Several 5,6-dialkyl-2,4-diarylpyrimidines were prepared and their electron
ionization (EI) mass spectra reported. The benzylic cleavage takes place ea
sily together with an important McLafferty rearrangement. The involvement o
f the nitrogen atom appears to be important in the fragmentation of 5-methy
l-substituted pyrimidines, In contrast, the 6-methyl-substitute pyrimidines
undergo benzylic cleavage without hydrogen transfer. Thus, the difference
in the mass spectrometric behaviour allows the identification of these isom
eric compounds which, in contrast, exhibit only small differences in their
NMR spectra. Copyright (C) 1999 John Whey & Sons, Ltd.