Reductive coupling of polyfunctionalized organobismuth and organolead arylating reagents in the synthesis of benzopyran derivatives

Benzopyran derivatives were synthesized in good yields by the reactions of tris[2-(chloromethyl)phenyl]bismuth diacetate and 2-(halomethyl)aryllead triacetates with phenols and naturally occurring 4-hydroxycoumarins in the presence of bases according to a three-step one-pot procedure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2520–2529, November, 2005.     

Azoles and Azines: CXIX. Alkylation of 5,5'-(4-Nitrobenzylidene)bis(2-thiobarbituric) Acid and 5-(4-Nitrophenyl)-2,8-dithioxo-5,7,8,9-tetrahydro-2H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(1H,3H)-dione with Haloacetic Acids and Their Esters

5,5'-(4-Nitrobenzylidene)bis(2-thiobarbituric) acid and 5-(4-nitrophenyl)-2,8-dithioxo-5,7,8,9-tetrahydro-2H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(1H,3H)-dione, similar to unsubstituted 2-thiobarbituric acid, readily react with haloacetic acids and their esters to form regioselectively the S-alkylation products. The alternative routes fo 5,5'-(4-nitrobenzylidene)bis[(4-hydroxy-6-oxo-1,6-dihydropyrimidine-5,2-diyl)sulfanyl]diacetic acids, based on condensation of 4,6-dihydroxypyrimidin-2-ylthioacetic acid with carbonyl compounds followed by cyclodehydration to [(5-(4-nitrophenyl)-4,6-dioxo-3,5,6,7-tetrahydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-2,8-diyl)di(sulfanyl)]diacetic acid derivatives, are less efficient. Alkylation of 2-thiobarbituric acid with ethyl bromoacetate in ethanol in the presence of alkali yields 5-(2-oxo-2,5-dihydro-1,3-thiazol-4-yl)-2-thiobarbituric acid.     

Interdiffusion and phase equilibrium in systems based on cellulose nitrates and low-volatile solvents

Phase equilibrium and interdiffusion in systems based on cellulose nitrates with different contents of nitrogen and several organic solvents, such as ethyl carbitol, dimethyl carbonate, and diethyl carbonate, have been studied. Cellulose nitrate containing 12.2 wt % nitrogen forms homogeneous systems with all studied solvents over the entire composition range. Systems based on cellulose nitrate with a high content of nitrogen (13.2 wt %) possess limited compatibility with the solvents. Phase diagrams constructed for these systems testify to the fact that the region of homogeneous solutions widens with a decrease in temperature. For the system composed of cellulose nitrate containing 13.2 wt % nitrogen and ethyl carbitol, the lower critical mixing temperature is ?10°C. The presence of water in ethyl carbitol causes widening of the region of unstable solutions and leads to a reduction in the lower critical mixing temperature.     

Dynamic structure of organic compounds in solution according to NMR data and quantum chemical calculations: II. Styrene

The dynamic structure of styrene has been studied with the goal of obtaining detailed information on the internal rotation parameters. A potential energy surface has been constructed for the rotation of the vinyl group about the single bond in terms of the second-order Møller–Plesset perturbation theory with aug-cc-pvtz basis functions, and conformational dependences of ⁿ J _HH have been calculated at the FPT DFT (B3LYP) level of theory with basis functions of the same type. The vibration-averaged coupling constants have been compared with the experimental values reliably determined in this work. A high efficiency of the proposed dynamic model for structural studies of organic molecules with ultrafast internal rotation dynamics has been demonstrated.     

Synthesis of Perfluoroalkyl[1,2,4]triazolo[1,3]thiazinones

Russian Journal of General Chemistry -     

Cu-MOF-Catalyzed Carboxylation of Alkynes and Epoxides

The catalytic activity of copper-containing heterogeneous catalysts, in particular metal-organic frameworks, zeolites, and alumina-supported nanoparticles, in the carboxylation of terminal alkynes and oxiranes has been evaluated. Temperature dependences of these reactions have been studied.

     

Effects of phase equilibrium and the rate of mutual dissolution of reactants on the formation of polyurethane block copolymers

Interdiffusion and phase equilibrium in the region of amorphous separation were investigated by means of the microinterference technique at 20–130°C for a number of binary systems based on oligoesterdiol, butanediols, and diisocyanates—components of polyurethane block copolymers. The concentration dependences of interdiffusion coefficients in the mutual dissolution region were determined for all test systems. For systems composed of partially compatible components, the concentration limits of thermodynamically unstable solutions were established. By means of transmission electron microscopy, the structure of polymers synthesized both in the region of single-phase solutions of the reactants and in the phase separation region is assessed.     

Thermodynamic Properties of Hexamethylenetetrammonium Dodecahydro-<Emphasis Type="Italic">closo</Emphasis>-dodecaborate

The enthalpy of combustion of hexamethylenetetrammonium dodecahydro-closo-dodecaborate is determined via combustion in a KL-5 calorimeter and is found to be?17660 kJ/mol. Its standard enthalpy of formation is calculated using the obtained experimental data (?538 kJ/mol).