MASS-SPECTROMETRIC AND PYROLYTIC BEHAVIOR OF SOME ARYLSUBSTITUTED ISOXAZOLINES

The synthesis and mass spectrometric (MS) and pyrolytic behavior of th ree 3,5-aryl-substituted isoxazolinyl acetophenones, oxyphenyl)-3-phen yl-5-isoxazolyl]-1-phenylethanone (I), -3-phenyl-5-isoxazolyl]-1-(4-me thylphenyl)ethanone (II) and )-3-(4-methylphenyl)-5-isoxazoly]-1-pheny lethanone (III) are discussed. Compound I and the mixture of the isome ric compounds II and III were prepared by the reaction of 2,4,6-arylpy rylium salts with hydroxylamine. The substances were investigated usin g electron ionization, positive chemical ionization with methane and f ast atom bombardment. The isomeric compounds II and III were separated by gas chromatography (GC)/mass spectrometry. MS/MS and high-resoluti on MS were used to establish the fragmentation mechanisms. The thermal decomposition products obtained by off-line pyrolysis/GC/MS of I-III were compared with the MS fragments. The results of the investigation will facilitate the detection and identification of 3,5-aryl-substitut ed isoxazolinyl acetophenones in plant extracts. (C) 1998 John Wiley & Sons, Ltd.