Azines and Azoles: CXX. Synthesis of Acyclic Analogs of N1-Ribosides of Barbituric Acid and Its 5-ylidene Derivatives

The reaction of 2,4,6-tris(trimethylsiloxy)pyrimidine with 2-oxabutane-1,4-diyl diacetate in methylene chloride in methylene chloride in the presence of SnCl₄ proceeds regioselectively to form 1-[(2-acetoxyethoxy)methyl]barbituric acid. The latter is readily deacetylated to a free acyclic analog of N-ribosides of barbituric acid. 1-[(2-Acetoxy- and 2-hydroxyethoxy)methyl]barbituric acids easily react with aromatic and heterocyclic aldehydes in water and organic solvents, forming 5-ylidenebarbituric acids. The structure of the products was proved by ¹H NMR and UV spectroscopy. Certain of the products exhibit a moderate antimicrobial and antiviral activity.     

Investigation of azoles and azines. 75. Structure of 2-aryl-1,3-oxazine-4,6-diones in the gas phase

The mass-spectrometric fragmentation of a number of potentially tautomeric 2-aryl-1,3-oxazine-4,6-diones and model substances that fix the possible tautomeric forms was studied. The characteristic fragmentation pathways that are peculiar to one or another tautomer and the characteristic ions that make it possible to identify them in tautomeric mixtures were ascertained. It is shown that in the gas phase 2-aryl-1,3-oxazine-4,6-diones exist in mixtures of 4-hydroxy, 6-oxo, dipolar-ionic, and dicarbonyl forms; the amounts of the latter two forms increase with intensification of the electron-acceptor properties of the substituent in the para position of the benzene ring.See [1] for Communication 74.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 552–556, April, 1990.     

Study of azoles and azines. 78. Structure of 2-aryl-4,6-dioxo-1,3-thiazines in the crystalline state

For communication 77, see ref. [1].     

Thermodynamics of addition polymerization

Addition polymerizations of both acyclic and cyclic monomers show the characteristic features of any aggregation process, in particular, a ceiling temperature above which the formation of the aggregate (long‐chain polymer), under given conditions of monomer concentration, solvent, and pressure, would involve a positive change of free energy and is therefore impossible. Conversely, for a given temperature, pressure, and solvent, there is an equilibrium monomer concentration below which long‐chain polymer cannot be formed. Monomers must therefore have a negative free energy of polymerization, under given conditions, if they are to be capable of undergoing a significant extent of polymerization. The effect of monomer structure, including ring size, on thermodynamic polymerizability is discussed, as well as the possibility of copolymerizing monomers that cannot themselves give homopolymers. Examples are given for various possible mechanisms of polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2137–2146, 2000     

5,5'-Methylenebis(4,6-dihydroxy-2-methylthiopyrimidines)

5,5'-Methylenebis(4,6-dihydroxy-2-methylthiopyrimidines) were synthesized by condensation of 4,6-dihydroxy-2-methylthiopyrimidine with formaldehyde and aromatic or heterocyclic aldehydes in ethanol. According to the spectral data and PM3 quantum-chemical calculations, the most favorable tautomers of 5,5'-methylenebis(4,6-dihydroxy-2-methylthiopyrimidine) are those stabilized by intramolecular hydrogen bonds between the OH group of one pyrimidine fragment and the CÍO groups of the other.     

Azines and azoles: CXXIV. New synthesis of 2-oxochromene-3-carboxamides

2-Aryl-4-hydroxy-6H-1,3-thiazin-6-ones react with substituted 2-hydroxybenzaldehydes in polar solvents to give N-arylcarbothioyl-2-oxochromene-3-carboxamides in 60–70% yield.     

Condensation of Hydroxypyrimidines with Carbonyl Compounds: I. Barbituric Acids

Condensation reactions of barbituric acids with aldehydes, ketones, and their analogs, also with participation of C- and N-nucleophiles as third components, resulting in versatile pyrimidine-containing heterocyclic systems are considered.