New one-pot synthesis of spiro[furo[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine-6,5′-pyrimidine]pentaones and their sulfur analogues

Reaction of barbituric acid (BA), 1,3-dimethyl barbituric acid (DMBA) and 2-thiobarbituric acid (TBA) with cyanogen bromide and various aldehydes in presence of triethylamine afforded a new class of heterocyclic stable 5-alkyl and/or 5-aryl-1H, 1′H-spiro[furo[2,3-d]pyrimidine-6,5′-pyrimidine]2,2′,4,4′,6′(3H,3′H,5H)-pentaones which are dimeric forms of barbiturate (uracil and thiouracil derivatives) at 0 °C to ambient temperatures. Structure elucidation is proved by X-ray crystallography, ¹H NMR, ¹³C NMR, FT-IR, CHN and mass analyses techniques. Mechanisms of the formations are discussed.     

Preparation of novel pyrrol-2-one derivatives via an effective synthesis of new oxazole scaffold

A convenient procedure for the preparation of oxazole and pyrrole derivatives is described. 2-Amino-1,3-oxazol-2-ones 3a,b were first synthesized from the cyclocondensation reactions of cyanamide (2) with 4-ethoxycarbonyl-5-aryl-2,3-furandione 1a,b, and then new pyrrol-2-ones 5 were synthesized from the reaction of the compounds 3 with various aromatic amines 4.     

Unexpected simultaneous synthesis of trisubstituted quinolines and acylhydrazones under catalyst-free conditions

Trisubstituted quinolines and acylhydrazones were unexpectedly prepared from a reaction of N′-((2-aminophenyl)(phenyl)methylene)benzohydrazides with acetylenic esters. Using of N′-((2-aminophenyl)(phenyl)methylene)benzohydrazides led to obtain not only quinoline, but also a second pharmaceutical important product acylhydrazone. Notably, excellent yields, operational simplicity, short reaction times, and the avoidance of the use of catalysts make this approach an attractive complementary method to produce quinoline-2,3-dicarboxylates. The crystal structure of 5a was determined using single-crystal X-ray crystallography. The results showed that crystal packing diagram of 5a is of two pairs of molecules that have two independent alternate intermolecular 1D-polymeric H-bonds between two perpendicular molecules.     

Synthesis, spectral studies of salicylidine-pyridines: crystal and molecular structure of 2-[(1E)-2-aza-2-(5-methyl(2-pyridyl)ethenyl)]-4-bromobenzen-1-ol

Schiff bases derived from different meta-substituted salicylaldehyde and 5-methylaminopyridine have been synthesized and characterized by elemental analysis, FT-IR, NMR and UV-vis techniques. NMR assignments were made using (1)H, (13)C NMR and aided by 2D HETCOR and HMBC heteronuclear correlation techniques. The UV-vis spectra of the compounds were found useful in understanding the existence of tautomeric equilibria [phenol-imine (O-H...N) and keto-amine (O...H-N) forms] in polar and non-polar solvents. In order to rationalize the stabilization of tautomer in solid state, X-ray structure of 2-[(1E)-2-aza-2-(5-methyl(2-pyridyl)ethenyl)]-4-bromobenzen-1-ol (6) was determined. According to our crystallographic result, it has enol-imine tautomeric form.     

Regioselective synthesis of the 3,4-dihydrofuro[3,2-d]pyrimidin-2(1H)-one skeleton: a new class of compound

We hereby report the first preparation of the 3,4-dihydrofuro[3,2-d]pyrimidin-2(1H)-one skeleton formed by two controlled Curtius rearrangements of the corresponding acyl azides, prepared from 2-(2-methoxy-2-oxoethyl)furan-3-carboxylate via the hydrazide. Rearrangement of the acyl azides followed by trapping by nucleophiles and intramolecular trapping provided the target compounds.     

Boundary effects in local inflation and spectrum of density perturbations

We observe that when a local patch in a radiation filled Robertson–Walker universe inflates by some reason, outside perturbations can enter into the inflating region. Generally, the physical wavelengths of these perturbations become larger than the Hubble radius as they cross into the inflating space and their amplitudes freeze out immediately. It turns out that the corresponding power spectrum is not scale invariant. Although these perturbations cannot reach out to a distance inner observer shielded by a de Sitter horizon, they still indicate a curious boundary effect in local inflationary scenarios.     

4-(2-Methylphenyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione (I) and 4-(4chlorophenyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione (II)

The crystal and molecular structures of the title compounds have been determined by x-ray structure analysis. The compounds (I) and (II) crystallize in space groups P2₁2₁2₁ and 12/a respectively. The structures were solved by direct methods and refined to R = 0.058 and R = 0.046. The saturated pyrimidine-2-one ring in both structures deviates from the planarity. There are two intermolecular hydrogen bonds in (I) and (II). The configuration at C4 in (I) is S.     

Synthesis and spectral properties of new hetarylazo indole dyes

A series of new hetarylazo indole dyes were synthesized by azo coupling of 2-phenyl-, 2-methyl-, and 1-methyl-1-phenyl-1H-indole with diazonium salts derived from 5-methylsulfanyl-1H-1,2,4-triazol-3-amine, 1H-1,2,4-triazol-3-amine, 5-methylisoxazol-3-amine, and 5-amino-1,3,4-thiadiazole-2-thiol. The dyes were characterized by the IR spectra, electronic absorption spectra in the UV and visible regions, and ¹H NMR and mass spectra. The effects of solvent nature, acidity of the medium, temperature, and concentration on the electronic absorption spectra in the visible region and the dependence of the color of the dyes on the nature of heterocyclic fragment were examined. Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 7, pp. 1041–1047. The text was submitted by the authors in English.     

Synthesis, characterization and spectroscopic properties of some new phenylazo-6-aminouracil

In this study, a series of new 5-phenylazo-6-aminouracil dyes were prepared by linking m-,p-nitroaniline, m-,p-chloroaniline, m-,p-anisidine, m-,p-toluidine, m-,p-cyanoaniline, p-ethoxyaniline, p-phenoxyaniline, p-ethylaniline, p-acetamidoaniline, p-acetylaniline, p-carboxyaniline and aniline to 6-aminouracil. The prepared dyes were characterized by UV-vis, FT-IR, ¹H NMR spectroscopic techniques and elemental analysis. The effect of acid and base upon the UV-vis spectra of these dyes were investigated. In addition, the solvatochromic behaviors and substituent effects in various solvents were evaluated.