Mass Spectra of New Heterocycles: XXVI. Electron Impact and Chemical Ionization Study of N-[5-Amino-2-thienyl]- and N-[2-(Methylsulfanyl)-1,3-thiazol-5-yl]isothioureas

Abstract

The behavior of a representative series of previously unknown N -(5-amino-2-thienyl)- and N -[2-(methylsulfanyl)-1,3-thiazol-5-yl]isothioureas under electron ionization (70 eV) has been studied for the first time. 2-Thienylisothioureas form a fairly stable molecular ion ( I rel 11-25%), whereas there are no peaks of molecular ions in the mass spectra of 1,3-thiazolylisothioureas. The common direction of the decay of the molecular ion of 2-thienyl- and 1,3-thiazolylisothiourea is the breaking of the C-N bond in the isothiourea fragment with the localization of the charge on the imine nitrogen atom and the formation of the ion [R3SC≡NR2]+ ( I rel 34-100%), and for thienyl derivatives also the ion [ M - R3SC=NR2]+ (with the localization of the charge on the amine nitrogen atom). Moreover, the last ion is the main one ( I rel 91-100%). Peaks of [ M - MeSCN]+• and [MeSCS]+ ions have also been identified in the spectra of 1,3-thiazolylisothioureas, the appearance of which is associated with the decay of the thiazole cycle in a molecular ion. In addition, unlike 2-thienylisothioureas, for the studied 1,3-thiazolylisothioureas, there is a break in the Chet-N bond with the localization of the charge on the thiazole-containing fragment.