Synthesis and mass spectrometry of some arylidene-hydrazinyl-thiazolines and their 2-arylidene-N-(3-chlorophenyl)hydrazinecarbothioamide precursors

Abstract

N-(3-Chlorophenyl)hydrazinecarbothioamide (2) was prepared by reacting 1-chloro-3-isothiocyanatobenzene (1) with hydrazine hydrate in 2-propanol, whose 1 H-NMR spectrum showed its existence in a Zwitter ionic betain form. A number of 2-arylidene-N-(3-chlorophenyl)hydrazinecarbothioamides (3a-e) were synthesized by the condensation of 2 with aromatic aldehydes in absolute ethanol and in the presence of a catalytic amount of glacial acetic acid. They were reacted with 2-bromo-1-(4-bromophenyl)ethanone (4) in 2-propanol/DMF in the presence of anhydrous potassium carbonate to produce the respective 2-(arylidenehydrazono)-4-(4-bromophenyl)-3-(3-chlorophenyl)-2,3-dihydrothiazoles (5a-e) in excellent yields. The synthesized compounds were characterized by spectroscopic methods as well as mass spectrometry. The molecular modeling and atomic charges of heteroatoms in all compounds were performed using Chem3D Pro 12.0.2 software and provided an excellent tool to investigate the fragmentation pathways. The nitrogen rule was also found to be good predictors of molecular ions and their fragmentation patterns.