Azines and Azoles: CXXII. New Regioselective Synthesis of 1-Substituted 6-Alkyluracils

Readily available 5-acyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-diones with primary alkyl- and arylamines in mild conditions (boiling in propan-2-ol) to give Schiff bases. In more rigid conditions (boiling in DMF), the reaction is accompanied by COS liberation and provides 1-substituted 6-alkyluracils. This previously unknown reaction possesses a considerable synthetic potential and can be considered as a new, general, and regioselective synthetic approach to 1-substituted 6-alkyluracils.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 146–158.Original Russian Text Copyright © 2005 by Yuskovets, Moskvin, Mikhailov, Ivin.For communication CXXI, see [1].     

Azines and azoles. 64. Mass spectra and tautomerism of 2-aryl-4,6-dioxo-1,3-thiazines

Mass spectra of 2-aryl-4,6-dioxo-1,3-thiazines were studied and the general fragmentation paths of these compounds determined. Based on mass spectra of compounds with fixed structures, 2-aryl-5,5-dialkyl-4,6-dioxo-1,3-thiazines, 4-alkoxy- and 4-acyloxy-2-aryl-6-oxo-1,3-thiazines, the decomposition paths of the dicarbonyl and hydroxycarbonyl forms were determined. It was concluded on the basis of the obtained data that 2-aryl-4,6-dioxo-1,3-thiazines exist in the gas phase predominantly in the hydroxycarbonyl form.For Communication 63, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1409–1412, October, 1987.     

Research in the pyrimidine series XXV. Calculation of the normal vibrations of barbituric and 2-thiobarbituric acids

The frequencies and forms of the in-plane normal vibrations of the tricarbonyl forms of barbituric and 2-thiobarbituric acids and their tetradeutero derivatives were calculated. The calculations were made for the C_zv (or C_2v and C_s for barbituric acid) symmetry point group. The principal frequencies observed in the IR spectra of these compounds were assigned with respect to the types of vibrations on the basis of an analysis of the forms of the normal vibrations.     

Relative reactivities of some dienes and acetylenes in copolymerization with sulfur dioxide

The reactivities of isoprene, piperylene,2,3-dimethylbutadiene, hex-1-yne, and phenylacetylene, at ?20°C, relative to that of cyclohexene, have been determined for the radical-initiated copolymerization with sulfur dioxide to form 1:1 polysulfones. The unsaturated hydrocarbons were copolymerized with sulfur dioxide in pairs and the composition of the terpolymers determined from the 100 MHz NMR spectra. The dienes react 11–15 times as fast as hex-1-ene, while hex-1-yne reacts 16 times more slowly. Phenylacetylene reacts 21 times as fast as hex-1-yne. The relative reactivities are interpreted mainly in terms of the effect of electron delocalization on the stability of the product radical.     

Azoles and azines. 62. Structure of 2-aryl-1,3-oxazine-4,6-diones

¹H,¹³C NMR, IR, and UV spectra have been studied for solutions of a number of potentially tautomeric 2-aryl-1,3-oxazine-4,6-diones and their 5-methyl substituted analogs with variation of substituent at the para position of the benzene ring, as well as compounds with a fixed structure that simulates possible tautomeric forms. The data have been compared with the results of quantum chemical calculations carried out in SSO MO LCAO approximation by the CNO, CNDO/2, and MPNDO/3 methods. In DMSO and THF solution the test compounds exist predominantly as 2-aryl-4-hydroxy-6H-1,3-oxazin-6-ones. The para substituent in the benzene ring does not affect the composition of the tautomer mixture significantly.For Communication 61, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 386–394, March, 1987.     

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.     

Thermodynamics of Addition Polymerization Processes

The polymerizability of compounds such as 1,l-disubstituted ethylenes, aldehydes, ketones, isocyanates, and five- and six-membered ring compounds is determined largely by thermodynamic considerations. The transition from non-polymerizability to polymerizability, correspondlng to a change in the sign of ΔG, is often quite sharp. Factors which generally make the free energy of polymerization more negative, and which therefore favor polymerization, are low temperature, high pressure, and high monomer concentration. Additional driving force is sometimes available if the monomer is in the supercooled (glassy) state rather than the crystalline state, or if the polymer crystallizes on formation. Alkyl substituents have an unfavorable effect on polymerizability; halogen substituents have a favorable effect. Many monomers which do not homopolymerize for thermodynamic reasons will copolymerize with a second monomer to the extent of forming copolymers containing 50 or even 66 mol per cent of the first monomer.     

Mass transfer in non-steady-state hydride epitaxy of Si1−x Gex/Si structures

Numerical simulation of the non-steady-state kinetics for the solid solutions MBE-grown from silane and germane with vapor sources was carried out. The smearing of the germanium distribution at the interfaces in the Si_1?x Ge_x/Si structures was studied both in the absence of the atomic fluxes in the reactor and in their presence (the “hot-wire” method). It is shown that the use of an additional hot source enhances the growth. Moreover, at gas pressures exceeding 10^?3 torr (provided that the gas flow remains molecular) and at growth temperatures T _gr<600°C, such conditions can minimize the width of the transition regions at the interfaces.