Refernces
10.1007/BF00506677
The research focuses on the isomerization of thiazolo[4,5-b]quinoxalines in the presence of acids, investigating the pathways of their isomerizational transformations and the influence of the R1 substituent on the process. The purpose of the study was to understand the rearrangement of these compounds and to explore the possibility of converting them into other five-membered heterocycles. The researchers concluded that the isomerization proceeds through a step involving dissociation to a quinoxalinium cation and the corresponding thioamide, and that the stability of the thiazolo[4,5-b]quinoxalines in an acidic medium is a key factor in their isomerizational transformations. The chemicals used in this process included 4-alkyl-2-phenylthiazoloquinoxalines, 2,4-dimethyl-3a,4,9,9a-tetrahydrothiazolo[4,5-b]quinoxaline, and various acids such as acetic acid, trifluoroacetic acid, and hydrochloric acid, as well as phenylthiourea for the conversion to imidazo[4,5-b]quinoxaline-2-thione.
10.1134/S1070363208100228
The study investigates the reaction of thiourea and various substituted thioureas with 1,3-dibromopropyne to synthesize different thiazolidine derivatives. The chemicals involved include thiourea, N-phenylthiourea, N,N'-diphenylthiourea, N-acetylthiourea, and 1,3-dibromopropyne. These reactants are used to produce 4-bromomethylidene-2-imino(phenylimino, acetylimino)-1,3-thiazolidine hydrobromides and 4-bromomethylidene-2-acetylimino-1,3-thiazolidine under different solvents and temperature conditions. The study explores the reaction mechanism, which likely involves the formation of intermediate bromoethynylmethylsulfides that cyclize into the final thiazolidine products. The products' structures are confirmed through elemental analysis and IR, 1H and 13C NMR spectroscopy data.
10.1039/c6ra05385h
The study presents a visible light promoted, catalyst-free synthesis of thiazoles and imidazo[2,1-b]thiazoles in an EtOH:H2O green medium. The key chemicals involved are phenacyl bromide, N-phenylthiourea, and 2-aminothiazole. Phenacyl bromide serves as a reactant that undergoes homolytic fission of its C-Br bond under visible light, generating a free radical. N-phenylthiourea also forms a free radical through the homolytic fission of its S-H bond. These radicals combine to form intermediate compounds, which further react to produce the desired thiazoles and imidazo[2,1-b]thiazoles via cyclization and removal of a water molecule. The use of visible light provides the activation energy needed for the reaction, eliminating the need for catalysts or photosensitizers. The EtOH:H2O solvent system enhances the solubility of the reactants and stabilizes the transition states, contributing to the eco-efficiency and high yield of the products. This method is notable for its cost-effectiveness, short reaction time, and alignment with green chemistry principles.
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