New Aspects of the Reaction of Thioacetamide and N-Substituted Maleimides.

N-Arylmaleimides are universal substrates for the synthesis of various heterocyclic compounds with a wide spectrum of biological activity. However, their reactions with thioacetamides have not been comprehensively studied. We studied the reactions of thioacetamide with N-arylmaleimides under various conditions. We established for the first time that three types of products: epithiopyrrolo[3,4-c]pyridines, pyrrolo[3,4-c]pyridines and 3,3'-thiobis(1-arylpyrrolidine-2,5-diones) can be obtained in different conditions. In all cases, two maleimide molecules are involved in the reaction. 3,3'-Thiobis(1-arylpyrrolidine-2,5-diones) are the major products when the reaction is conducted at boiling in acetic acid. When thioacetamide and N-arylmaleimide are kept in dioxane at 50 °C, epithiopyrrolo[3,4-c]pyridines can be isolated, which, when heated in dioxane, in acetic acid or in methanol in the presence of catalytic amounts of sodium methoxide, are converted into pyrrolo[3,4-c]pyridines by eliminating hydrogen sulfide. The reaction of thioacetamide and N-arylmaleimide in dioxane at boiling temperature with the portioned addition of N-arylmaleimide leads predominantly to the formation of pyrrolo[3,4-c]pyridines. The reaction of thioacetamide with N-alkylmaleimides under all the above conditions leads predominantly to the formation of the corresponding sulfides. The structure of the compounds obtained was characterized by a set of spectral analysis methods and X-ray diffraction (XRD) data.

Analysis of the spectral-luminescence properties of imidazo[1,2-b]pyrido[4,3-e][1,2,4]triazin-6(7Н)-ones.

The article presents a method for the construction of a new tricyclic system of imidazo[1,2-b]pyrido[4,3-e][1,2,4]triazin-6(7Н)-ones based on subsequent reactions of the obtained 1,2-diamino-4-phenylimidazole ethyl ether of 3-methyl-6-phenylimidazo[1,2-b][1,2,4]triazin-2-carboxylic acid with dimethylformamide dimethyl acetal and primary amines. The structures of the obtained compounds were confirmed using the data obtained from 1 Н and 13 С NMR, HRMS, and XRD analyses. We analyzed the dependence of the absorption and photoluminescence spectra on the structure of the compounds obtained using quantum chemistry methods. The theoretical results were compared with the data from a real experiment. The article suggests a range of practical applications for imidazo[1,2-b]pyrido[4,3-e][1,2,4]triazin-6(7Н)-ones.