Preparation of individual derivatives in 1,3-oxazino[5,4,3-ij]quinolines and 1,4-oxazino[2,3,4-ij]quinolines series by column chromatography and their mass spectrometric study

Abstract

Hundreds of highly effective compounds that have a complex of practically useful properties are known among tricyclic hydroquinolines. Therefore, the production of new compounds of high purity in this series and identification of the features of their behaviour under the influence of electron impact for the determination of their structures is important. Previously, we synthesized 1,3-oxazino[5,4,3-ij]quinoline-1,3-diones and 1,4-oxazino[2,3,4-ij]quinoline-2,3-diones, but the nature of the mass spectral decay for the determination of their structures was not discussed. In this study, using thin-layer chromatography, it was shown that during the synthesis of these compounds by-products can be formed, for which conditions for purification using column chromatography were selected. Fundamental differences were discovered in the stability of the studied isomeric compounds under the influence of electron impact and in the nature of fragmentation of their molecular ions. 1,4-oxazino[2,3,4-ij]quinolines were more resistant to electronic impact, the peak intensities of their molecular radical ions ([M]+•) were much higher than those of 1,3-oxazino[5,4,3-ij]quinolines, while the hydroquinoline fragment was much more stable than both the 1,3-oxazine and 1,4-oxazine rings. The presence of a multiple bond in the hydropyridine ring of the compounds reduced the intensity of the [M]+• peak. For compounds containing heme-dimethyl groups at the α-carbon (relative to the nitrogen atom) atom, the intensity of the [M]+• peak was minimal due to the ease of elimination of the methyl radical from it, especially if this led to aromatization of the quinoline fragment. Defragmentation of the oxazine cycle of 1,3-oxazino[5,4,3-ij]quinolines starts with the elimination of a carbon dioxide molecule, and defragmentation of1,4-oxazino[2,3,4-ij]quinolines starts from elimination carbon monoxide molecules. The discovered patterns of decomposition (EI) can be used to identify similar derivatives of condensed 1,3- and 1,4-oxazines and tricyclic hydroquinolines annealed at the i and j bonds.