Interaction of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-α]pyrimidine with methylene-active compounds and acid hydrolysis of its products

Reactions of 2-bromo-7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine with sodium derivatives of pentane-2,4-dione, malonodinitrile, Meldrum acid, acetoacetic, cyanoacetic and malonic esters have been shown to give the respective substituted derivatives. Azinyl-ylidene tautomerism has been found to be characteristic of these compounds, the latter existing mainly in the ylidene form. The acid hydrolysis of pentane-2, 5-dione and cyanoacetic and malonic esters derivatives has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1961, November, 1993     

4-羟基香豆素及其衍生物的简便合成及其荧光性质的研究

用米氏酸和苯酚在无溶剂条件下以90.6%的收率合成丙二酸单苯基酯, 然后用Eaton试剂(五氧化二磷＋甲基磺酸)在温和条件下闭环, 以78.8%的收率得到4-羟基香豆素, 将这种方法扩展合成了苯环上带有各种取代基的4-羟基香豆素衍生物以及4-羟基硫代香豆素衍生物. 并对部分4-羟基香豆素衍生物的荧光性质进行了研究.     

Synthesis of zwitterionic salts via three-component reactions of pyridacylpyridinum iodide, aromatic aldehydes, and Meldrum acid or N,N-dimethylbarbituric acid

New zwitterionic salts of pyridinium-Meldrum acid and pyridinium-barbituric acid are conveniently synthesized from the three-component reactions of 2-, 3-, or 4-pyridacylpyridinum iodides, aromatic aldehydes, and Meldrum acid or N,N-dimethylbarbituric acid in the presence of triethylamine as base promoter in acetonitrile.     

New spiro-fused 2-nitrocyclopropanecarboxylates: Synthesis and structure

Reactions of alkyl 3-bromo-3-nitroacrylates with cyclic CH-acids, Meldrum’s acid or 3-methyl-1-phenylpyrazol-5-one, afford new spiro-fused 2-nitrocyclopropanecarboxylates. In the case of Meldrum’s acid, the products are formed as individual diastereomers. The obtained experimental results are confirmed by quantum chemical calculations (B3LYP/6-311+G(d,p) taking into account solvent effects).     

Rh(Ⅰ)-catalyzed regio-and enantioselective allylic alkylation of Meldrum's acid

A Rh(Ⅰ)-catalyzed highly regio-and enantioselective allylic alkylation of Meldrum acid with racemic allylic substrates bearing alkyl groups has been developed.The applying of chiral bisoxazopinephosphine ligand is essential for the high yields and selectivities.This method provides a rapid access to various chiral β-alkyl-γ,δ-unsaturated carboxylic acids and their derivatives.     

An efficient regioselective sonochemical synthesis of novel 4-aryl-3-methyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-ones

An efficient ultrasound-assisted preparation of a series of novel 4-aryl-3-methyl-4,5-dihydro-l//-pyrazolo[34-b]pyridin-6(7H)ones via the reaction of 5-amino-3-methyl-1H-pyrazole,Meldrum’s acid and various arylaldehydes using one-pot three-component approach is described.This rapid method produced the products in short reaction times(3-4 min) and excellent yields(87-95%).     

Molecular diversity of triphenylphosphine promoted reaction of electron-deficient alkynes and arylidene Meldrum acid (N,N'-dimethylbarbituric acid)

The three-component reaction of triphenylphosphine, dimethyl hex-2-en-4-ynedioate and arylidene N,N'-dimethylbarbituric acids in dry methylene dichloride at room temperature afforded trans-1,3-disubstituted 7,9-diazaspiro[4.5]dec-1-enes in good yields and with high diastereoselectivity. However, the similar three-component reaction with arylidene Meldrum acids resulted in a mixtures of cis/trans-1,2-disubstituted 7,9-dioxaspiro[4.5]dec-1-enes. Additionally, the three-component reaction of triphenylphosphine, dimethyl but-2-ynedioate and arylidene Meldrum acids gave polysubstituted 5-(triphenyl-λ⁵-phosphanylidene)cyclopenta-1,3-dienes. A plausible reaction mechanism was proposed for the formation of various products with different regioselectivity and diastereoselectivity.     

New thermosets obtained from DGEBA and Meldrum acid with lanthanum and ytterbium triflates as cationic initiators

Ytterbium and lanthanum triflates were used as cationic initiators to cure mixtures of diglycidylether of bisphenol A (DGEBA) and Meldrum acid (MA) in several proportions of comonomers and initiators. The evolution of epoxy and lactone groups during curing, and of linear ester formed in the final materials were evaluated by Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR).

The global evolution of the curing process was investigated by calorimetric analysis and the activation energy was calculated by isoconversional procedures.

Shrinkage on curing and thermal degradability of the final materials on varying the initiator and the proportion of Meldrum acid in the mixtures were evaluated. The expandable character of MA was confirmed. The materials obtained were more degradable than conventional epoxy resins due to the tertiary ester groups incorporated into the network by copolymerization, especially those obtained with ytterbium triflate. On increasing the proportion of initiator the degradability was also increased.     

Catalyst-free synthesis of 1,2,4,5-tetrasubstituted imidazoles from arylamins,benzonitriles, arylglyoxals,and Meldrum’s acid

An efficient and catalyst-free for the synthesis of 1,2,4,5-tetrasubstituted imidazoles has been developed using a one-pot, two-step reaction of arylamins, benzonitriles, arylglyoxals, and Meldrum’s acid. All the products were obtained in good to excellent yields and their structures were established from their spectroscopic data.     

Acyl/aroyl Meldrum’s acid as an enol surrogate for the direct organocatalytic synthesis of α,β-unsaturated ketones

The operationally simple, robust and straightforward organocatalytic protocol is developed for the synthesis of E-selective α,β-unsaturated ketones. The method utilizes simple and easily accessible starting materials such as Meldrum’s acid, carboxylic acid, aldehyde and simple bifunctional amine catalyst. The tandem organocatalytic process utilizes acyl/aroyl Meldrum’s acid as an enol surrogate for the effective Doebner-Knoevenagel type condensation reactions. A wide variety of aldehydes, carboxylic acids and base sensitive functional groups are well tolerated under the mild reaction conditions.