Synthesis and molecular structure of 1,4-dimethyl-4,5,7,8-tetrahydro-6H-imidazo[4,5-e][1,4]-diazepine-5,8-dithione

1,4-dimethyl-4,5,7,8-tetrahydro-6H-imidazo[4,5-e][1,4]-diazepine-5,8-dithione was synthesized by boiling 1,4-dimethyl-4,5,7,8-tetrahydro-6H-imidazo[4,5-e][1,4]-diazepine-5,8-dione (a cyclic homolog of theobromine) with P₂S₅. Its molecular and crystal structures were determined by X-ray structure analysis, PMR spectroscopy and the calculations using the MM2 program. The crystals are monoclinic, sp. gr. P2 ₁ /n with a=9.305(4), b=9.464(3), c=11.628(3) Å, -90.49(3)^o, Z=4 for C₈H₁₀N₄S₂. M.p. 268–269 °C. The 7-membered heterocycle has a boat conformation in the crystal, while in solution at room temperature it undergoes interconversion. The geometrical parameters of the molecule obtained by X-ray structure analysis, by PMR spectroscopy below the coalescence temperature (290 K), and by MM2 calculations are in good agreement.A. V. Bogatsky Physico-Chemical Institute, Ukrainian Academy of Sciences. Translated fromZhurnal Struktumoi Khimii, Vol. 34, No. 3, pp. 86–90, May–June 1993.Translated by T. Yudanova.     

Hybrid resins from polyisocyanate/vinyl ester/water glass systems: Structure and properties

Polysilicate modified polyurea/vinyl ester hybrid resins were produced by dispersing water glass (WG) in a mixture of vinyl ester (VE) and polyisocyanate in presence of a liquid phosphate as emulsifier. As styrene-crosslinkable VE resins bisphenol A (BA) and novolac types (N), whereas as polyisocyanate a polymeric methylene diphenyl isocyanate (PMDI) were used. The structure and selected properties of the hybrid resins were determined and compared to those of the neat VEs and polysilicate filled polyurea (denoted as 3P resin). Using VE for resin hybridization, which worked as an additional emulsifier for the WG/PMDI/phosphate system, resulted in a fine particle dispersion of the polysilicate. It was found that the type of VE affected not only the dispersion of WG (and thus of the polysilicate) but also the network formation of the polyurea/VE hybrids and their properties. Information about the structure of the polysilicate filled hybrid resins was gained from dynamic-mechanical thermal analysis (DMTA), scanning electron and atomic force microscopic measurements. It was argued that the resin hybridization yielded a conetwork instead of an interpenetrating one. The properties of the hybrid systems were determined by DMTA, fracture mechanical tests, thermogravimetric analysis and flammability measurements. It was established that the stiffness and resistance to thermal degradation of the initial 3P resin was strongly improved by hybridization with VEs. The fracture toughness (K_c) proved to be less sensitive to the formulation of the hybrid resins. On the other hand, the fracture energy (G_c) and limiting oxygen index experienced a positive deviation from the additivity as a function of the 3P/VE composition, at least in a given range.     

Synthesis and heterocyclization of 3-aryl-2-methyl-2-thiocyanatopropanamides

Reactions of arenediazonium tetrafluoroborates with methacrylamide in the presence of potassium thiocyanate in aqueous acetone (1: 2.5) or aqueous dimethyl sulfoxide (1: 4) gave the corresponding 3-aryl-2-methyl-2-thiocyanatopropanamides which underwent heterocyclization in boiling acetic anhydride to produce difficultly accessible 2-(acetyl)amino-5-benzylthiazol-4(5H)-ones.     

Reaction of 6‐Methyl‐2‐Thiouracil and 6‐Phenyl‐2‐Thiouracil with Chloro‐β‐Dicarbonyl and Bromo‐β‐Dicarbonyl Compounds and Their Nitrile Analogs

Derivatives of 2‐methylidene‐1,3‐dihydropyrimidin‐4‐ones 2a , 2b , 2c , 2d , 2e , 2f , 2g were synthesized by interaction of 6‐methyl‐2‐thiouracil and 6‐phenyl‐2‐thiouracil 1a , 1b with some activated halogenides: diethyl bromomalonate, ethyl 2‐chloro‐3‐oxobutanoate, ethyl 2‐bromocyanoacetate, 2‐bromo‐5,5‐dimethylcyclohexan‐1,3‐dione, and bromomalononitrile. The boiling of 1a with ethyl 2‐bromocyanoacetate in mixture of ethanol and EtONa results in intramolecular cyclization and formation of thiazolo[3,2‐a]pyrimidin‐5‐one 3 . Interaction of 1a with 3‐chloropentane‐2,4‐dione and 2‐bromo‐1,3‐diphenylpropane‐1,3‐dione yielded corresponding S‐substituted thiopyrimidines 4a , 4b . In general, the products of 1b S‐alkylation are less prone to sulfur extrusion. Reaction of 1b with diethyl bromomalonate in the absence of EtONa stops at the S‐alkylation step, while in the presence of EtONa in ethanol or PPh₃ in dioxane 2‐(ethoxycarbonylmethyl)thio‐6‐phenyl‐1,3‐dihydropyrimidin‐4(1H)‐one 6 is formed exclusively. Molecular structure and crystal structure of 2‐(1,1‐diethoxycarbonylmethyliden)‐6‐methyl‐1,3‐dihydropyrimidin‐4(1H)‐one 2a are discussed.     

Formation of star-like water-soluble polymeric structures in the process of radical polymerization of N-isopropylacrylamide in the presence of C60

Russian Chemical Bulletin - The formation of star-like N-isopropylacrylamide (NIPA) polymeric structures in the presence of C60 occurs in two steps. In the polymerization induction period,...     

Note on the motion of black holes

It is shown that from the point of view of a distant observer the gravitational field of a moving Schwarzschild black hole is the same as produced by an extended, non-rotating, spherical body of the same mass. According to him, a black hole follows the Newtonian equations of motion, though some quantities, for example the distance, lose their Newtonian meaning.     

Synthesis of 5-arylsubstituted thiazol-4-one acetyl and amino derivatives by the heterocyclization of the products of acrylamide thiocyanatoarylation

The heterocyclization of 2-thiocyanato-3-arylpropionamides in acetic anhydride followed by the deacylation of the intermediates formed in an alkaline medium afforded the otherwise difficultly accessible 2-amino-5-benzylthiazol-4-ones.     

A simple approach to the synthesis of 2-(2-amino-4-arylthiazol-5-yl)pyrimidines

The synthesis of 2-(2-amino-4-arylthiazol-5-yl)pyrimidin-4(3H)-ones from the available 2-(2-oxo-2-arylethylidene)-2,3-dihydropyrimidin-4(1H)-ones was developed.