ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
[M — H+]- ions of isoxazole (la), 3-methylisoxazole (1b), 5-methylisoxazole (1c), 5-phenylisoxazole (1d) and benzoylacetonitrile (2a) are generated using NICI/OH- or NICI/NH2- techniques. Their fragmentation pathways are rationalized on the basis of collision-induced dissociation and mass-analysed ion kinetic energy spectra and by deuterium labelling studies. 5-Substituted isoxazoles 1c and 1d, after selective deprotonation at position 3, mainly undergo N — O bond cleavage to the stable α-cyanoenolate NC — CH = CR — O- (R = Me, Ph) that fragments by loss of R—CN, or R—H, or H2O. The same α-cyanoenolate anion (R = Ph) is obtained from 2a with OH-, or NH2-, confirming the structure assigned to the [M — H+]- ion of 1d, On the contrary, 1b is deprotonated mainly at position 5 leading, via N—O and C(3)—C(4) bond cleavages, to H—C ≡ C— O - and CH3CN. Isoxazole (1a) undergoes deprotonation at either position and subsequent fragmentations. Deuterium labelling revealed an extensive exchange between the hydrogen atoms in the ortho position of the phenyl group and the deuterium atom in the α-cyanenolate NC — CD = CPh — O-.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210240709
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