One-pot synthesis of pyrimidines under solvent-free conditions

N,N,N’,N’-Tetrabromobenzene-1,3-disulfonamide was used as an efficient catalyst for the one-pot synthesis of pyrimidine derivatives in excellent yields from triethoxymethane, ammonium acetate, and various ketone derivatives at 100–110 °C under solvent-free conditions.     

One-pot synthesis of xanthene derivatives under solvent-free conditions

One-pot synthesis of aryl-14H-dibenzo[a,j]xanthene and 1,8-dioxo-octahydroxanthene derivatives using montmorillonite K10 as reusable eco-friendly catalyst under solvent-free conditions is described.     

Thermal isomerization of 3,3-dimethylcyclopropene under adiabatic-compression conditions

The thermal isomerization of 3,3-dimethylcyclopropene under adiabatic-compression conditions at 660–850 K occurs in two independent directions with the formation of isopropylacetylene and isoprene; kinetic parameters for each of these routes were obtained. The formation of products of the gem-dimethylvinylcyclopropanation of olefins during their copyrolysis with 3,3-dimethylcyclopropene is not observed, apparently because of the occurrence of isomerization of 3,3-dimethyl-cyclopropene in the gas phase at 660–850 K without the participation of gemdimethylvinylcarbene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2008–2010, September, 1989.The authors thank A. I. Ioffe and N. V. Volchkov for participation in the discussion of the obtained results.     

Transformations of secondary diacetylenic alcohols under alkaline isomerization conditions

Summary A study was made of the transformation of secondary diacetylenic alcohols in alkaline medium and the structure of the vinylacetylenic keto alcohols obtained here was proved.Translated from Izvestiya Akademii Nauk SSSR, Khimicheskaya, No. 12, pp. 2215–2216, December, 1965     

n-Butane isomerization in the gas phase and under supercritical conditions

The aromatization of n-butane under supercritical conditions on gallium-, zinc-, and platinum-modified high-silica zeolites with a modulus of 30–70 was first studied, and the experimental data were compared to the results of a study of this process in the gas phase. It was found that the operational efficiency of catalysts for n-butane conversion under supercritical conditions was much higher than that for the gas-phase reaction in terms of activity, productivity, and resistance to poisoning by condensation products. The aromatization of gaseous n-butane at 530°C and 1 atm was characterized by rapid catalyst deactivation. The selectivity for the benzene-toluene-xylene (BTX) fraction was higher than 50%. Under supercritical conditions at 430–560°C and 100–200 atm, the selectivity of formation of aromatic compounds decreased by a factor of 2, whereas the yield of C₁-C₃ cracking products increased by the above factor. On the other hand, it was found that an increase in the productivity of catalysts by a factor of 20–50 with the retention of almost 100% activity for several days of operation is an advantage of the process performed under supercritical conditions. The almost complete conversion of butane under supercritical conditions was found on promoted HZSM-5 zeolite samples. The thermogravimetric analysis of spent samples suggested a higher degree of catalyst carbonization under supercritical conditions, as compared with that in the reaction performed in the gas phase. However, the deposition of 20–30 wt % condensation products on the catalysts had no detectable effect on the high activity of the catalysts in the reaction performed under supercritical conditions.     

无溶剂“一锅法”催化合成氨甲酸酯基烷基萘酚衍生物

无溶剂条件下,对甲基苯磺酸亚铈可有效催化2-萘酚、醛和氨基甲酸酯三组分"一锅法"合成氨甲酸酯基烷基萘酚衍生物。考察了溶剂条件、原料配比、催化剂用量和反应温度对产率的影响。经催化剂循环研究,该催化剂重复使用3次仍保持较高活性。产物的结构通过熔点、IR、1H NMR、13C NMR、质谱和元素分析进行测定和结构表征。同时给出了该反应可能的反应机理。     

One-pot sequential synthesis of 1,2-disubstituted benzimidazoles under metal-free conditions

An easy and inexpensive method has been developed to access 1,2-disubstituted benzimidazoles following a one-pot sequential coupling/reduction/cyclization process under metal-free neutral conditions.     

One-pot multicomponent synthesis of polyhydroquinolines under catalyst and solvent-free conditions

Abstract

An efficient one-pot condensation has been developed for the synthesis of polyhydroquinolines via a four component coupling reaction of aldehyde, dimedone, ethyl acetoacetate, and ammonium acetate under catalyst and solvent-free conditions. Non-hazardous experiment procedure, operational simplicity, mild reaction conditions, and the compatibility with various functional groups represent the advantages of the present method.     

Iridium-catalyzed isomerization of primary allylic alcohols under mild reaction conditions

The isomerization of primary allylic alcohols into the corresponding aldehydes has been accomplished using an analogue of Crabtree’s iridium hydrogenation catalyst and by adequately tuning the experimental conditions. A wide range of substrates is converted quantitatively into the desired aldehyde at room temperature in expedient reaction times by using catalyst loading as low as 0.25 mol %.     

One-pot three-component Mannich reaction catalyzed by iodine under solvent-free conditions

One-pot three-component Mannich reactions of ketones with aromatic aldehydes and aromatic amines are effectively catalyzed by molecular iodine at room temperature under solvent-free conditions to afford the corresponding β-amino carbonyl compounds with moderate to excellent yields. The method has the following advantages: no use of solvent, mild condition, high reaction speed and small quantity of catalyst.     

亚临界水脱除煤中硫的实验研究

近年来,超临界流体以其独特的性质作为溶剂或反应介质在众多领域得到应用。对于煤在超临界及亚临界水中的行为研究也越来越受到国内外学者的重视,如Kashimura等、Hu等和Cheng等对褐煤在亚临界及超临界水中的降解行为进行了研究。Timpe等报道了水热处理对年轻煤中有机硫及微量元素的脱除行为。     

One-pot synthesis of 2-amino-3-cyanopyridine derivatives under solvent-free conditions

A series of 2-amino-3-cyanopyridines were obtained from aryl aldehydes, substituted acetophenones, malononitrile and ammonium acetate in good to excellent yields by proceeding through a simple, mild and efficient procedure utilizing N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] and poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) [PBBS] as catalysts.     

One-pot preparation of fluorinated propargylamines under microwave irradiation and solvent-free conditions

A facile one-pot method has been developed for the synthesis of fluorine-containing propargylamines by a three-component coupling of fluorinated aldehydes, amines, and alkynes, in the presence of copper (I) chloride under microwave irradiation and solvent-free condition. This process is an efficient alternative to traditional thermal reaction. All new compounds are fully characterized by spectral methods.     

Degradation of crosslinked unsaturated polyesters in sub-critical water

The degradation of unsaturated polyesters crosslinked with styrene was performed in sub-critical water (SCW) in the absence and presence of organic additives. The unsaturated polyesters were de-crosslinked by hydrolysis of ester chains to form polystyrene derivatives on SCW treatment at 300 °C. With an increase in treating time, carboxylic acid groups in the polystyrene derivatives were turned into carboxylic anhydride groups in SCW. The de-crosslinking rate was much enhanced on SCW treatment in the presence of hydroxy compounds with a long alkyl chain and alkylamines, while carboxylic acids, benzenesulfonate salts, and quaternary ammonium salts were ineffective even though they had a long alkyl chain. The degree of de-crosslinking was reduced in the presence of diamines and amino acids because re-crosslinking at both ends of the additive molecules proceeded.     

Gold-catalyzed isomerization of unactivated allenes into 1,3-dienes under ambient conditions

We have developed a gold-catalyzed isomerization of unactivated allenes into 1,3-dienes with nitrosobenzene as an additive. This reaction proceeded almost exclusively at room temperature for highly substituted allenes. The utility of this reaction is manifested by the development of one-pot [4+2]-cycloaddition of allenes and reactive alkenes.     

Crossflow filtration of washed and unwashed yeast suspensions at constant shear under nominally sub-critical conditions

Operation at sub-critical fluxes can be used to control membrane fouling. The original definition of the critical flux stated that operation was sub-critical if no or negligible fouling occurred. Over time there has been a relaxing of the criteria and many now consider a low rather than zero rate of fouling to be indicative of sub-critical operation especially when dealing with complex feeds. Here the region of low fouling is termed “nominally sub-critical”. Unwashed yeast, washed yeast and extra polymeric substance (EPS) suspensions were filtered at controlled fluxes to investigate the role of cells and soluble components in nominally sub-critical conditions using ultrafiltration (UF) and microfiltration (MF) membranes. As the UF membrane could not be effectively cleaned it was not used in the later part of the study. Tracking of membrane resistance, of the 0.2 μm membranes was continued through the whole study. After the initial increase, rises very slowly, increasing on average only 0.4% after each experiment and cleaning cycle. For the MF membranes, the rate of fouling increased with increasing feed concentration, increasing membrane pore size and decreasing shear stress. The effect of increasing shear stress was to reduce the amount of reversible fouling but the irreversible component was invariant with shear stress for the range studied. Also the rate and reversibility of fouling were found to be sensitive to changes in pH. The sum of the rates of transmembrane pressure (TMP) rise for washed yeast cells and EPS suspensions were in all cases found to be lower than that for unwashed yeast. The origin of the additional resistance is discussed and other relevant literature reviewed.     

One-pot dehydrogenation of carboxylic acid derivatives to α,β-unsaturated carbonyl compounds under mild conditions

Carboxylic acid derivatives such as N-acyl-2-oxazolidones, δ-lactones, and δ-lactams were smoothly dehydrogenated to the corresponding α,β-unsaturated carbonyl compounds in one-pot manner at −78 °C just by treating their lithium enolates with N-tert-butylbenzenesulfinimidoyl chloride.     

One-pot synthesis of polysubstituted indoles from aliphatic nitro compounds under mild conditions

Polysubstituted indoles can be prepared directly from functionalized nitroalkanes under very mildly acidic conditions in a simple, one-pot, two-stage procedure.