Mass-Spectra of New Heterocycles: XXIX. Study of 2-(Alkylsulfanyl)quinolines by Electron Ionization

The properties of a representative number of previously unknown 2-(alkylsulfanyl)quinolines, obtained from aryl isothiocyanates, allene or acetylene carbanions, and methyl iodide, upon electron ionization (70 eV) have been studied for the first time. All the studied compounds form a stable molecular ion, which is clearly detected in the mass spectra. All studied quinolines are characterized by common decay patterns, including the formation of M – H, M – Me, and M – HS ions. The main effect on fragmentation is exerted by the nature of substituents at positions 3 and 4 of the pyridine cycle of quinolines. The molecular ion of 4-methyl-2-(methylsulfanyl)-3-(1H-pyrrol-1-yl)quinolines electron ionization undergoes rearrangement, which occurs both with the participation of a sulfur atom and with the participation of a carbon atom of the methyl group in the 4 position of the heterocycle. Ways of fragmentation of the formed ions of the studied 2-(alkylsulfanyl)quinolines are proposed based on the analysis of the mass spectra of daughter ions.