Direct sulfonylation of pyrazolones with sodium sulfinates catalyzed by TBAI in water

An efficient sulfonylation reaction of pyrazolones with sodium sulfinates catalyzed by TBAI was established. A wide variety of valuable sulfonated pyrazolones were obtained in good to excellent yields using water as solvent.     

Practical synthesis of bicyclic pyrazol-5-one derivatives

This communication describes a convenient synthesis of fused bicyclic pyrazolones in a one-pot reaction procedure. Modified protocols are also developed to access 5,5-bicyclic and bulky pyrazolones in good yields. The method reported herein represents a practical approach to structurally diversified bicyclic pyrazolones.     

Efficient di-bromination of 5-pyrazolones and 5-hydroxypyrazoles by N-bromobenzamide

An efficient and convenient method for the bromination of pyrazolones and 5-hydroxypyrazoles was developed by using N-bromobenzamide in THF at room temperature. This new method provided di-bromimated pyrazolones in excellent yields (≥90%).     

Reactions of hydroxyazolidines with π-donor heterocycles. 2. Reaction of 1-acetyl-5-hydroxypyrazolidines with pyrazol-5-ones on the surface of adsorbents

The reaction of 1-acetyl-2-phenyl-5-hydroxypyrazolidines with pyrazol-5-ones leads to the corresponding 4-(pyrazolidin-5-yl)pyrazolones, which exist mainly in the form of hydroxypyrazoles. The process proceeds on the surface of adsorbents in a nonpolar solvent. The structure and stereochemistry of the bisheterocycles obtained were studied.For Communication 1, see [1].M. V. Lomonosov Moscow State University, Moscow 119899, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1079–1087, August, 1998.     

Analytical characterization of some pyrazolones and their copolymers with some vinyl compounds

Some new pyrazolones have been synthesized and their copolymers with styrene, methylmethacrylate and methacrylic acid prepared. The pyrazolones and their styrene and methylmethacrylate copolymers are insoluble in water but form chelate complexes with some alkaline-earth and transition metal ions. The water-soluble methacrylic acid copolymers do not form complexes with these elements, however, probably because of hydrogen-bonding of the chelating groups to the methacrylic acid carboxyl groups. Special attention was paid to the complexation of Au(III), which was assumed to proceed mainly through the nitrogen atoms of the pyrazolone ring.     

Asymmetric Synthesis of Spiropyrazolones by Rhodium‐Catalyzed C(sp2)−H Functionalization/Annulation Reactions

Rhodium‐catalyzed C(sp²)−H functionalization reactions of 4‐aryl‐5‐pyrazolones followed by [3+2] annulation reactions with alkynes provide rapid access to highly enantioenriched five‐membered‐ring 4‐spiro‐5‐pyrazolones. The use of a chiral SCpRh catalyst enabled the synthesis of a large range of spiropyrazolones with all‐carbon quaternary stereogenic centers in up to 99 % yield and 98 % ee from readily available substrates.     

Steric effect of ortho-substituents of 1-phenyl-3-methyl-4-aroyl-5-pyrazolones on the synergic extraction of lutetium with trioctylphosphine oxide

The substituent effect of ortho-substituted 4-aroyl derivatives of 1-phenyl-3-methyl-5-pyrazolones (HA) on the adduct formation reaction between their lutetium chelates and a neutral ligand, trioctylphosphine oxide (TOPO, L), in benzene was studied using a liquid-liquid extraction system. The lutetium 4-aroyl-5-pyrazolonates react with TOPO to form LuA₃L and LuA₃L₂ types of adducts. An obvious steric hindrance of the terminal group on the adduct formation reaction was observed. Linear relationships between the acid dissociation constant of the ortho-substituted 4-aroyl-5-pyrazolone derivatives and those of the corresponding benzoic acids, between the extraction constants of lutetium and the acid dissociation constants of pyrazolones and between the adduct formation constants of TOPO and the acid dissociation constants of pyrazolones could be obtained.     

Adamantane and its derivatives. 1. Hydrazones and pyrazolones of adamantane

The dihydrazones, bis(diphenylhydrazones), and bis (2,4-dinitrophenylhydrazones) of adamantanone-2-carboxylic acid, dimethyl adamantane-2,6-dione-1,5-dicarboxylate, and tetramethyl adamantane-2,6-dione-1,3,5,7-tetracarboxylate and the pyrazolones of the corresponding acids were synthesized. It is shown that the methyl esters of adamantane-2,6-dione-1,5-dicarboxylic and -1,3,5,7-tetracarboxylic acids and their hydrazones cannot be converted to adamantane-1,5-dicarboxylic and -1,3,5,7-tetracarboxylic acids under the conditions of the Huang-Minlon and Locke reactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 528–531, April, 1982.     

Quantum-chemical investigation of structure and reactivity of pyrazol-5-ones and their thio- and seleno-analogs: X. Solvent effect on the chemical shifts of nuclei in the molecules of 3-methylpyrazol-5-ones and 1-phenyl-3-methylchalcogenepyrazol-5-ones and characteristics of tautomeric equilibrium in these compounds

By quantum-chemical DFT/GIAO method chemical shifts of all nuclei in the NMR spectra of 3-methylpyrazol-5-one and 1-phenyl-3-methylchalcogenopyrazol-5-ones in chloroform and dimethyl sulfoxide were calculated and analyzed using various solvation models. Low sensitivity to solvent of the chemical shfts of ¹³C and ¹H nuclei (except for “acidic” protons) calculated in the framework of various continuum models is revealed. Discrete and discrete-continuum models reflect well deshielding of the active centers of H-complexation and chemical shifts of “acidic” protons of the studied pyrazolones in solutions. Optimization of geometry of pyrazolones in solutions only slightly improves the agreement between the theoretically calculated and the experimental values. Shielding of nitrogen, oxygen, sulfur, and selenium atoms is more sensitive to the nature of solvent and to the nature of tautomeric forms. The methods of NMR spectroscopy allow to identify reliably the dominating tautomeric form but they are insufficient for the quantitative characterization of tautomeric equilibria.     

Azines and Their Acyclic Derivatives as Transferers of One-carbon Fragment in Reactions with Pyrazolones

Enehydrazine derivatives have been obtained by the reaction of 6-phenyl-1,2,4-triazine 4-oxide with pyrazolones 2, which on further heating with pyrazolones 2 are converted into the corresponding symmetrical or unsymmetrical derivatives of dipyrazolylmethane. Enehydrazine derivatives of 1,3-dimethyl-5-nitrosouracil and 1,3-dimethylimidazolidine interact with 3-methyl-1-phenyl-5-pyrazolone (2a) with the formation of dipyrazolylmethane derivative. On interacting compound 2a or 3-methyl-1-(p-nitrophenyl)-5-pyrazolone with 3,6-diphenyl-1,2,4-triazine 4-oxide 12 the corresponding 4,4'-bispyrazolones are formed, but the interaction of compound 12 with 3-(p-nitrophenyl)-1-phenyl-5-pyrazolone leads to dipyrazolylmethane derivative. Dipyrazolylmethane derivative is obtained on heating of fervenulin 4-oxide, 2,4-dihydroxy-5-nitropyrimidine, and 1,3,5-triazines: 6-azauracil, 5-azauracil, azacytosine, and 2,4-diamino-s-triazine with pyrazolone 2a.     

A detailed investigation into the one-pot cascade reaction of ethyl 3,9-dimethyl-7-phenyl-6H-dibenzo-[b,d]pyran-6-one-8-carboxylate with phenylhydrazine

Research on Chemical Intermediates - When synthesizing cyclohexane-annulated pyrazolones from a cyclohexonedicarboxylate derivative with phenylhydrazine under the catalysis of sulfuric acid in the...     

A novel route to 4‐oxy/thio substituted‐1H‐pyrazol‐5(4H)‐ones via efficient cross‐Claisen condensation

α‐Oxy/thio substituted β‐keto esters were synthesized through an efficient cross‐Claisen condensation of oxy/thio substituted acetic acid ethyl esters with acid chlorides, which in turn converted in situ into 4‐oxy/thio substituted‐1H‐pyrazol‐5(4H)‐ones by the addition of hydrazine and its derivatives. This method has been found to be extremely fast, general, and useful toward the synthesis of inaccessible pyrazolones and synthetically demanding 4‐oxy/thio substituted pyrazolones. J. Heterocyclic Chem., (2011).     

Base-Catalyzed Synthesis of Spiropyrazoloaminonitriles with Arylidene Pyrazolone and Vinylogous Malononitriles through a Cascade Michael Addition and Cyclization

Synthesis of title compounds were accomplished by a reaction of vinyl malononitriles and arylidene pyrazolones catalyzed by base. This protocol proceeds via Michael addition followed by intramolecular cyclization leading to the formation of two new C−C bonds. Further the same reaction was also conducted with α,α-dicyano olefins and vinyl malononitriles to furnish 1,6-dihydro biphenyl compounds. Simple reaction conditions, high yields and compatibility are the advantages of this protocol.     

Highly Z-selective asymmetric conjugate addition of alkynones with pyrazol-5-ones promoted by N,N'-dioxide-metal complexes

Highly selective: the title reaction is achieved with high enantiomeric and geometric control and thermodynamically unstable (Z)-enone derivatives are obtained as the major products. The procedure tolerates a wide range of substrates to generate optically active pyrazolones with vinyl-substituted quaternary stereocenters.     

Asymmetric,Three‐Component,One‐Pot Synthesis of Spiropyrazolones and 2,5‐Chromenediones from Aldol Condensation/NHC‐Catalyzed Annulation Reactions

A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3‐diketones, 2,5‐chromenediones are available through [2+4] annulation.     

Waste-Free Solid-State Organic Syntheses: Solvent-Free Alkylation,Heterocyclization, and Azo-Coupling Reactions

Summary. Solid-state techniques allow for waste-free quantitative syntheses. The solid–solid reactions of α-haloketones with several pyrazolones and with thiosemicarbazones were shown to afford the corresponding pyrazolyl ethers and 4-substituted 2-(arylidenehydrazino)thiazoles. The product yields are quantitative in all cases and the products do not require purifying workup. Therefore, these reactions are truly solvent-free, sustainable, and no wastes are produced. A diazonium nitrate is quantitatively accessible by gas–solid reaction of the corresponding amine with NO₂ gas. It is a useful material for environmental synthesis of azo dyes through solid-state coupling with a variety of coupling compounds, as e.g. β-naphthol, acetoacetanilide, pyrazolones, and barbituric acid.     

Waste-Free Solid-State Organic Syntheses: Solvent-Free Alkylation, Heterocyclization, and Azo-Coupling Reactions

Solid-state techniques allow for waste-free quantitative syntheses. The solid–solid reactions of α-haloketones with several pyrazolones and with thiosemicarbazones were shown to afford the corresponding pyrazolyl ethers and 4-substituted 2-(arylidenehydrazino)thiazoles. The product yields are quantitative in all cases and the products do not require purifying workup. Therefore, these reactions are truly solvent-free, sustainable, and no wastes are produced. A diazonium nitrate is quantitatively accessible by gas–solid reaction of the corresponding amine with NO₂ gas. It is a useful material for environmental synthesis of azo dyes through solid-state coupling with a variety of coupling compounds, as e.g. β-naphthol, acetoacetanilide, pyrazolones, and barbituric acid.     

Organocatalytic asymmetric one-pot sequential reaction: synthesis of highly substituted spirocyclohexanepyrazolones with six contiguous stereogenic carbons

An atom-economical synthesis of chiral polyfunctionalized spiropyrazolone derivatives based on the development of a new organocatalytic enantioselective one-pot sequential Michael/Michael/Aldol reaction of 1,3-dicarbonyl compounds with unsaturated pyrazolones and α,β-unsaturated aldehydes has been developed. The notable features of this one-pot sequential process include the generation of up to six consecutive stereogenic carbon centers including one quaternary stereocenter and five tertiary stereocenters with high enantioselectivities (up to 95% ee) and excellent diastereoselectivities (>99:1 d.r.).     

Electrolytical enrichment for liquid scintillation determinations of low tritium samples: A revised methodology

The determination of carbon, hydrogen, nitrogen, fluorine, chlorine and sulphur contents for characterization of plutonium complexes with organic ligands have been standardized and glove box adopted. Various plutonium(IV) mono- and di-carboxylates, plutonium(IV) chelates with pyrazolones, UO ₂ ⁺⁺ and PuO ₂ ⁺⁺ complexes having pyrazolones as chelating agent and sulfoxides, amides and phosphine oxide ligands as oxodonors; uranium carbides and uranium nitrides and several potential organic extractants for actinides were analyzed satisfactorily. All these methods set up in double module glove box train are extremely useful for a low budget radioactive laboratory engaged in research in solid actinide complexes.     

Palladium-Catalyzed Asymmetric [4+2] Cycloaddition of 2-Methylidenetrimethylene Carbonate with Alkenes: Access to Chiral Tetrahydropyran-Fused Spirocyclic Scaffolds

A palladium-catalyzed asymmetric [4+2] cycloaddition of 2-methylidenetrimethylene carbonate with alkenes derived from pyrazolones, indandione, or barbiturate has been successfully developed, affording pharmacologically interesting chiral tetrahydropyran-fused spirocyclic scaffolds. The target compounds were generated in good to excellent yields and with high enantioselectivity (up to 99 % ee). Furthermore, this cycloaddition reaction could be efficiently scaled up, and several synthetic transformations were accomplished for the construction of other useful chiral spiropyrazolone and spiroindandione derivatives.