ELECTRON-IMPACT IONIZATION MASS-SPECTROMETRY AND INTRAMOLECULAR CYCLIZATION IN 2-SUBSTITUTED PYRIMIDIN-4(3H)-ONES

Electron impact ionization mass spectrometry indicates that the behavi or of N-unsubstituted pyrimidin-4-ones with CH2-R type substitution at C-2 differs from homologs that are N-substituted and/or 2-aryl- or 2- methyl-substituted. A dominant intramolecular cyclization was found to occur between 3N (in agreement with the predominance of the 3NH tauto mers) and the ortho positions of the aryl moiety in compounds with a C H2-aryl substitution at C-2. Theoretical calculations with an AM1 SCFR method on 2-, 6-, and 2,6-disubstituted pyrimidin-4-ones support the mass spectrometric observations.