Oxidation of bis-arylacetylhydrazones of α-dicarbonyl compounds

Oxidation of the title compounds (IV) with lead tetraacetate gives, instead of the expected 1-(α-arylacetyloxyarylethyleneamino)-1,2,3-triazoles, the amides (V), 1-(N-arylacetylamino)-1,2,3-triazoles, as the main products in moderate yields. The reaction mechanism is discussed.     

Synthesis of quinoxalines by cyclization of α-arylimino oximes of α-dicarbonyl compounds

The tandem 1,3 cycloaddition–rearrangement and open chain reactions of 2-aryl-N-aroyl-4,5-dimethyl-1,2,3-triazol-1-imines with DMAD at room temperature and in refluxing toluene are described.     

Reaction of ninhydrin with β-dicarbonyl compounds

The reactions of ninhydrin ( 1 ) with β-ketoesters and β-diketones were studied. Two kinds of products were observed, which were either simple adducts of the dicarbonyl compounds to the center carbonyl group of ninhydrin, or tricyclic indeno[1,2-b]furans. Treatment of methyl 3-aminocrotonate ( 2 ) with ninhydrin led in analogous fashion to an indeno[1,2-b]pyrrole ( 3 ) which was reduced to a complex tetracyclic dihydropyridine 12 . A mechanism for the production of 12 is presented. Structures for the novel heterocycles are supported by high resolution nmr studies and X-ray crystallography.     

The lead tetraacetate oxidation of bisacetylhydrazones of α-dicarbonyl compounds

The oxidative cyclization of the title compounds results in generally two different kinds of products. The first, 1-(N,N-bisacetylamino)-1,2,3-triazole 7 (R³ = CH₃) is the primary product, while the second, 1-N-acetylamino-1,2,3-triazole 8 (R³ = CH₃), when observed, is obtained via hydrolysis from the former during work-up and separation of the reaction mixture. The primary products are considered as resulting from intramolecular nucleophilic attack on the acetyl group, of the presumed zwitterionic intermediate 5 (R³ = CH₃), by the N of the ambident N-acetylimine site of 5 .     

Condensation of o-aminophenol and α-dicarbonyl compounds. Part 1. Benzoxazines

By condensation with o-aminophenol of a series of phenylglyoxal derivatives two species of products were obtained, namely 2-hydroxy-(2H)-1,4-benzoxazines (I) and 2′ -aryl-2,2′ -dibenzoxa-zolines (II). The structure of compounds I was investigated by ir, uv and pmr spectroscopy and a reaction mechanism was proposed. J. Chem. Soc., 14, 997 (1977)     

Condensation of o-aminophenol and α-dicarbonyl compounds. Part 2. Dibenzoxazolines

The study of 2′-aryl-2,2′-dibenzoxazolines (II), obtained together with 2-hydroxy-(2H)-1,4-benzoxazines (1) by condensation of o-aminophenol with a series of phenylglyoxal derivatives, emphasized that these compounds are an equilibrium mixture of dibenzoxazolines and related tautomeric ketimine forms. This behaviour was widely investigated by ir, uv and pmr spectroscopy. J. Heterocyclic Chem., 14, 957 (1977)     

NMR study of the influence of β-substituents on the intramolecular hydrogen bond in β-dicarbonyl compounds

The hydroxyl proton chemical shifts of β-dicarbonyl compounds involving various β-substituents have been studied. An additive influence of β-substituents on the δ_OH shift values has been found. The results obtained suggested the existence of only one potential proton energy minimum in the intramolecular hydrogen bond of the enol forms of the β-diketones. It has been shown that the enol forms of β-keto esters do not follow the additivity of the δ_OH values for the same substituents, which may be due to a change in the proton distribution potential function in the intramolecular hydrogen bond.     

Zeolite-catalyzed three-phase hydration of α-pinene

In this paper, the kinetics, the product distributions and the corresponding reactions of some products of zeolite-catalyzed hydration of α-pinene have been studied. The results indicate: 1. α-Pinene is hydrated mainly to borneol, but isomerizations always accompany the hydration and camphene and limonene are the main olefines formed. 2. The disappearance of α-pinene follows the first-order kinetics, of which the rate constants, the activation energy as well as the activation entropies have been calculated. 3. A probable mechanism has been proposed, in which the hydration of α-pinene through two equilibrating adsorbed intermediates, which, via three pathways, lead to derivatives of fenchane, bornane and p-menthane respectively. The distributions of the three pathways have been examined and appear to be determined by the stability of the adsorbed intermediates themselves     

Isoxazolium enolates derived from α,β-unsaturated and 1,3-dicarbonyl compounds. The through-space effect of the enolate moiety on the chemical shift of α-protons

The reaction of 4-phenyl-3,5-dihydroxyisoxazole with α,β-unsaturated cyclic ketones and 1,3-cyclic diketones was studied. β-Substituted α,β-unsaturated ketones give pairs of isomeric isoxazolium enolates. The remarkable influence of the heterocyclic betaine on the proton chemical shifts is discussed. 1,3-Cyclic diketones reacted spontaneously with 4-phenyl-3,5-dihydroxyisoxazole yielding isoxazolium enolate enols and enol ethers.     

Tautomeric equilibrium of ketonic and cis- and trans-enolic forms of β-dicarbonyl compounds in solution

In this paper the tautomeric equilibrium of ketonic and cis- and trans-enolic forms of β-dicarbonyl compounds is considered as an acid-base protolytic one. The application of the Brønsted-Izmaylov theory has enabled to suggest a general equation K_TS = for keto-enol equilibrium constant, depending on the solvent, the well known Meyer's equation being included in it as a particular case. Equilibrium constants have been bromometrically determined in a number of solvents of keto-enols of three types, i.e. “cis-fixed”, “trans-fixed” and that involving both stereo-isomeric forms. A method for quantitative determination of cis-trans-enol equilibrium had been proposed.     

Carbon-proton coupling constants in α-chlorostyrene-α-13C

The two stereochemically distinct two-bond carbon-13- hydrogen coupling constants J(¹³C? CH), for α-chlorostyrene-α-¹³C have been shown to be of similar magnitude but opposite sign (?6.3 and +5.6 Hz). A simple additivity relationship which adequately reproduces all the reported J(¹³C? CH) values for chloroethylenes has been found.     

Condensation of 2-aminophenols and α-dicarbonyl compounds. Part 3. Benzoxazines substituted with heterocycles

A series of 1,4-benzoxazines (I) and 2,2′-dibenzoxazolines (II) were obtained by condensation of 2-aminophenol and 2-amino-5-nitrophenol with glyoxal derivatives of the heterocyclic series. The structure of compounds (I) was investigated by uv, pmr and mass spectroscopy.     

Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

Functional derivative δE/δρ in calculation of chemical potential for the Kohn–Sham electronic system

A method for finding the chemical potential for an electronic system with density ρ = Σ_ρi represented within the Kohn–Sham approximation is proposed. To find the chemical potential of the system under consideration, we propose to refer to the definition μ = δE/δ_ρ and to apply the mathematical properties of functional derivatives. Particularly, in the case examined, the result μ = μ( r ) ≠ const has been obtained, which may be explained in the framework of the calculus of variation. Taking the limit lim_r→∞ μ( r ) as the best approximation to the proper equilibrium chemical potential of a free atom, one obtains μ = ?I, where I denotes first ionization energy. A possibility of further applications of the proposed method in relation to crystalline systems is also discussed. © 1994 John Wiley & Sons, Inc.     

Condensation of 2-aminophenols and α-dicarbonyl compounds. Part 4. Dibenzoxazolines substituted with heterocycles

The tautomeric structure of 2,2′-dibenzoxazolines 2′-substituted with heterocycles was investigated by ir, pmr and uv spectroscopy.     

Investigation on the condensation of α and β ketoaldehydes with hydroxyaromatic compounds

Mechanism of the condensation reactions of methylglyoxal, phenylglyoxal and benzoylacetaldehyde with phenolic compounds have been discussed. It was observed that the reaction mechanisms changed depending on the type of the phenolic and also dicarbonyl compounds. While, methylglyoxal gave the angular methyl derivative of naphthofuraranonaphthofuran with 2‐naphthol, phenylglyoxal and its p‐chloro and p‐methoxy derivatives formed benzo[b]naphtho[2,1‐f]oxepine‐13‐ones. However, resorcinol behaved different and gave 2‐phenyl‐3‐(2,4‐dihydroxy)‐6‐hydroxy‐benzo[b]furans with phenylglyoxal derivatives. 2‐Phenyl‐4‐(2‐hydroxynaphmyl)‐4H‐naphtho[b]pyran was produced from the reaction of benzoylacetaldehyde and 2‐naphthol, but the reaction product was 3,9‐dihydroxy‐6‐phenyl‐6,12‐methano‐12H‐dibenzo[1,3]dioxocin when the same carbonyl compound reacted with resorcinol.     

H NMR titration and quantum calculation for the inclusion complexes of styrene and α-methyl styrene with α, β and γ-cyclodextrins

The inclusion behavior between styrene (α-methyl styrene) and cyclodextrins (CDs) was studied by using ¹H NMR titration in solution. The results indicate that 1:1 inclusion complexes were formed. The association constants of the inclusion complexes were determined by nonlinear least-square method. The inclusion process was also studied by using PM3 quantum-mechanical semi-empirical method. The calculated results are in agreed with the experimental data.