Reaction of tert-butylimine of phenylpropiolic aldehyde with substituted imidazole-2-thiones

Abstract

It has been shown earlier that the interaction of Ntert-butyl-1-aza-1,3-enes with substituted benzimidazole-2-thiols leads to the formation of polynuclear sulfur-containing heterocyclic compounds, viz., benzo [4,5]As a continuation of this research in the present work data are reported on the reaction of structural analogs of benzimidazole-2-thiols, viz., substituted imidazole-2-thiones, with phenylpropiolic aldehyde tert-butylimine (Scheme 1).The reaction proceeds under stirring at 60°C for 2 h. Target compounds IVa-IVc were isolated with yields of 50-70% as crystal compounds melting with the decomposition. Their structure was confirmed by the data of 1 H and 13 C NMR spectroscopy. Thus, in the 1 H NMR spectrum (IVa) the doublet at 6.26 ppm (J = 4.9 Hz) corresponds to the proton H 1 . The signal H 2 of the thiazine ring appears as a doublet at 6.66 ppm (J = 8.8 Hz). A doublet of doublets at 6.16 ppm (J = 8.8, 4.9 Hz) corresponds to the proton H 3 of the hydroxy group. Protons of two methyl groups and protons of aromatic rings appear in the typical regions.As in case of substituted benzimidazole-2-thiols [1, 2] the initially formed imidazo[2,1-b][1,3]thiazine-5tert-butylamines (IIIa-IIIc) undergo hydrolysis with the formation of imidazo[2,1-b][1,3]thiazin-5-ols (IVa-IVc). The hydrolytic cleavage of tert-bytylamine from imidazo[2,1-b]-[1,3]thiazine-5-tert-bytylamines (IIIa-IIIc) is due to the presence of minor quantities of water in the solvent [3].As a result of the addition of 4-phenyl-2-imidazole-2-thione (IIc) to imine I, the formation of two