Efficient microwave-assisted synthesis of 5-deazaflavine derivatives

A series of pyrimido[4,5-b]quinolines (5-deazaflavines), were synthesized by microwave assisted intramolecular cyclization. The N?-substituted-2,4-diamino-6-chloro-pyrimidine-5-carbaldehydes, were prepared by selective monoamination of 2-amino-4,6-dichloropyrimidine-5-carbaldehyde with aliphatic and aromatic amines.     

Acetonation of L-sorbose catalyzed by heteropoly acids

Acetonation of L-sorbose—a step of ascorbic acid synthesis—takes place in acetone to yield 85% of diacetone-L-sorbose in the presence of heteropoly acids H₃PW₁₂O₄₀ and H₄SiW₁₂O₄₀ (0.1–0.35%) as catalysts.

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L-— L- — -L- 85% 0.1–0.35% H₃PW₁₂O₄₀ H₄SiW₁₂O₄₀ .

     

Efficient ytterbium triflate catalyzed microwave-assisted synthesis of 3-acylacrylic acid building blocks

The derivatives of 4-(hetero)aryl-4-oxobut-2-enoic acid are useful as building blocks in the synthesis of biologically active compounds. An efficient general protocol for the synthesis of these building blocks was developed. This method combines microwave assistance and ytterbium triflate catalyst and allows the fast preparation of the target acids starting from different (hetero)aromatic ketones and glyoxylic acid monohydrate giving pure products in 52-75% isolated yields.     

Efficient microwave-assisted synthesis of highly functionalized pyrimidine derivatives

A generally applicable one-pot procedure for the rapid, easy, and diverse asymmetric functionalization of pyrimidines was developed that requires minimum efforts for the purification of the final products. 4-Amino-6-aryl-substituted pyrimidines are prepared in good yields by combined microwave-assisted amination and Suzuki-Miyaura cross-coupling reactions. The acid-mediated amination reaction affords the products as easily separable salts in 30-40 min reaction time.     

Supramolecular synthesis of coumarin derivatives catalyzed by a coordination-assembled cage in aqueous solution

A self-assembled Pd_4L_2 cage is employed as a water-soluble molecular flask for the synthesis of functionalized coumarins from a series of salicylaldehyde derivatives and cyanoacetates/malononitrile. The catalytic reaction features mild aqueous conditions and broad substrate scope. Crystal structures of the host-guest complexes for two substrates and one analogous intermediate have been obtained, shedding light on the supramolecular reaction mechanism. Michaelis-Menten kinetic studies were performed in one typical case, revealing that the rate of product formation has been enhanced by over 23-fold in contrast to the background reaction without cage. Moreover, the same reaction catalyzed by a smaller Pd_6L_4 cage gives a mixture of products and much lower yields, suggesting that fine-tuning on the size and symmetry of the cages' cavity is crucial for their applications in supramolecular catalysis.     

Efficient one-pot synthesis of benzoxazole derivatives catalyzed by Zinc triflate

A simple and efficient method has been developed for the synthesis of benzoxazoles from 2-aminophenol and substituted aldehydes in the presence of a catalytic amount of zinc triflate in ethanol solvent at reflux temperature.     

Efficient and selective microwave-assisted copper-catalyzed synthesis of quinazolinone derivatives in aqueous

Microwave-assisted copper-catalyzed cascade reactions between 2-halobenzoic acids and amidines to synthesize quinazolinone derivatives in water are reported. A variety of target products were obtained in good to excellent yields up to 94%. Its application was performed by the synthesis of 4-(1H-benzo[d]imidazol-2-ylthio)-6-methoxypteridine, which displayed significant anti-proliferation effect.     

Efficient enantioselective synthesis of 3-aminochroman derivatives through ruthenium-Synphos catalyzed asymmetric hydrogenation

A highly enantioselective asymmetric hydrogenation of various trisubstituted enamides derived from chroman-3-ones promoted by cationic Ru-Synphos catalysts is reported. This atom-economical and clean method provides an efficient route to optically active 3-aminochroman derivatives, which are important pharmacophores found in numerous drug candidates, in high chemical yields and enantiomeric excesses up to 96%.     

Synthesis of spirobiindanes via bis-cyclization reaction of the 1,5-diaryl-3-pentanones catalyzed by heteropoly acids

Bis-cyclization reaction of the 1,5-diaryl-3-pentanones catalyzed by heteropoly acids (HPAs) was examined for the first time, and a series of spirobiindanes were synthesized. 1,5-Diaryl-3-pentanones were refluxed and dehydrated in toluene in the presence of 0.15 equiv of a heteropoly acid to furnish spirobiindanes in moderate to high yield. For the known 4,4′-dibromo-7,7′-dimethoxy-1,1′-spirobiindane, the yield was upgraded from 66% to 80%.     

Mechanism of the liquid-phase oxidation of diethyl sulfide catalyzed by heteropoly acids

It has been established that in the oxidation of diethyl sulfide by¹⁸O₂ in CH₃C¹⁶O₂H–H₂ ¹⁶O solution at 369 K catalyzed by heteropoly acids, sulfoxide and sulfone with 44–54%¹⁸O enrichment are formed. The process is accompanied by isotope exchange of molecular oxygen.

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, ¹⁸O₂ CH₃C¹⁶O₂H–H₂ ¹⁶O 369 ¹⁸O 44–54%, .

     

Highly efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by heteropoly acids in water

<正>Heteropoly acids efficiently catalyzed the cyclocondensation reaction of anthranilamide with aldehydes in water at ambient temperature and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields.This method provides mild reaction conditions and clean reaction profiles,using a small quantity of catalyst and a simple workup procedure.     

Highly efficient one-pot three-component Mannich reaction in water catalyzed by heteropoly acids

[reaction: see text] Heteropoly acids efficiently catalyzed the one-pot, three-component Mannich reaction of ketones with aromatic aldehydes and different amines in water at ambient temperature and afforded the corresponding beta-amino carbonyl compounds in good to excellent yields and with moderate diastereoselectivity. This method provides a novel and improved modification of the three-component Mannich reaction in terms of mild reaction conditions and clean reaction profiles, using very a small quantity of catalyst and a simple workup procedure.     

Zeolite catalysed synthesis of coumarin derivatives

The direct synthesis of coumarin derivatives from m-substituted phenols and α,β-unsaturated carboxylic acids catalysed by solid-acid catalysts, such as zeolite H-Beta or Amberlyst-15, in toluene as solvent was studied. The conversion involves esterification followed by alkylation (ring closure). Ring closure of the ester is promoted both by an appropriate substituent on the aromatic ring and by Michael activation of the β-carbon of the ester. These influences were studied by variation of the reactants. 7-Hydroxy-3,4-dihydrocoumarin is formed in high yield when resorcinol and propenoic acid are used as reactants.     

Alkylation of hydroquinone with isobutene catalyzed by heteropoly acids in a two-phase system

The liquid-phase C-alkylation of hidroquinone with isobutene catalyzed by heteropoly acids H₃PW₁₂O₄₀, H₆P₂W₁₈O₆₂ and H₆P₂W₂₁O₇₁ (HPA) under phase-transfer conditions in a two-phase system, including toluene (upper phase) and HPA dioxane etherate, HPA·xC₄H₈O₁₂·yH₂O, (lower phase) has been studied.     

Syntheses of vitamins E and K1 catalyzed by heteropoly acids

Heteropoly acids H₃PW₁₂O₄₀ and H₄SiW₁₂O₄₀ have been found to be efficient catalysts for condensation of isophytol with 2, 3, 5-trimethylhydroquinone and 1-acetoxy-4-hydroxy-2-methyl-naphthalene in the syntheses of vitamins E and K₁, respectively.

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, H₃PW₁₂O₄₀ H₄SiW₁₂O₄₀ 2,3,5- 1--4--2- E K₁, .

     

Efficient synthesis of pyrimidinone derivatives by ytterbium chloride catalyzed Biginelli-type reaction under solvent-free conditions

An efficient and clean method was developed for the one-pot synthesis of pyrimidinones by ytterbium chloride catalyzed Biginelli-type reaction of aromatic aldehyde, cyclopentanone, and urea or thiourea under solvent-free conditions.     

n-Hexane cracking over heteropoly acids, 3. Silica supported heteropoly acids

Silica supported heteropoly acids are active in n-hexane cracking, while the pure compounds (except H₃PW₁₂O₄₀) are inactive. This result is explained by a partial transformation of H₆P₂W₁₈O₆₂ and H₆P₂W₂₁O₇₁ (H₂O)₃ into H₃PW₁₂O₄₀. In the case of H₄SiW₁₂O₄₀, the polyanion in interaction with silica leads to superacidic species upon thermal treatment.

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, , -, ( H₃PW₁₂O₄₀) . H₆P₂W₁₈O₆₂ H₆P₂W₂₁O₇₁ (H₂O)₃ H₃PW₁₂O₄₀. H₄SiW₁₂O₄₀ , , .

     

A novel synthesis of coumarin derivatives

The chemical behaviors of 3-ethynylcoumarin towards benzyl bromide,diazonium chic ride,hydrogen chloride,ethyl magnesium bromide and its self-coupling are reported.     

Efficient synthesis of 3-oxygenated benzothiophene derivatives

An efficient synthesis of 2-bromo-3-aryloxybenzothiophene derivatives by a conjugate addition-elimination sequence of 2,3-dibromo benzothiophene dioxides with phenolic nucleophiles has been developed. These benzothiophene derivatives serve as important intermediates for the synthesis of SERM analogues.     

Catalysis of the dealkylation of derivatives of 2,6-di-tert-butylphenol by heteropoly acids

Conclusions The tungsten heteropoly acids in acetic acid are the most active in the dealkylation of 4-alkyl-2,6-di-tert-butylphenols. The reaction is first order with respect to the substrate and with respect to the HPA, and water slows the reaction. It has been postulated that the dealkylation reaction is mediated mainly by the undissociated molecules of the HPA.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 752–756, April, 1987.