Improved Procedure for the Preparation of cis‐2,4‐Dimethylglutaranhydride

Addition of 2.5 mol% DBU to a mixture of isomeric 2,4‐dimethylglutaric anhydrides in ethyl acetate promotes crystallization‐induced transformation, affording the pure cis‐2,4‐dimethylglutaric anhydride in 87% yield.     

Influence of Preparation Conditions on the Catalytic Performance of MoNx/SBA-15 for Ammonia Decomposition

The influence of preparation conditions (e.g. H2-N2 ratios, final nitriding temperatures) on the performance of MoNx/SBA-15 catalysts for ammonia decomposition was investigated. The variation of catalytic activity with H2-N2 ratios may be attributed to the variation of surface compositions and particle sizes of the active components. The variation of nitriding temperatures leads to the formation of molybdenum nitride domains of varying compositions, which are responsible for the difference in their catalytic performance with respect to ammonia decomposition. At 923 K. ammonia could be completely decomposed using 15800 ml/h·gcat of GHSVNH,, which shows high performance for the catalytic decomposition of ammonia.     

An Improved and Convenient Procedure for the Synthesis of Ozagrel

Ozagrel 1 is a 1-alkylimidazole derivative that acts as a selective inhibitor ofthromboxane A2 (TXA2) with an IC50 of 11mol/L. The beneficial effects of TXA2inhibition by ozagrel include improved motor coordination after experimental stroke, andantihypert…     

Improved Procedure for the Detritylation of DMT-Oligonucleotides: Use of Dowex®

Dowex® resin (H⁺ form) is a convenient reagent for detritylation of 5′-O-DMT-oligonucleotides. With Dowex, detritylation is rapid and quantitative compared to that with acetic acid. As the liberated dimethoxytrityl species remain bonded to the resin, further processing of oligonucleotides is simplified.     

A Simple and Efficient Procedure for the Preparation of O-aryl-O-ethyl-S-allyl Thiolophosphates

HubeiNaturalScienceFoundationforfinancialsupportChap-cyethy-S-allylthiOlwioSPhates(2a-j)havePOtenhalbiologicalachvihes.Inl983,Y.TamaruandZYoshidarePOrtedPallatuxn(o)catalyZedthiono-ffooloallylicrearr~mentOfcrallylphoSPhoro-andphoSPhonotheonaes,andaiSOreinvestigaedthennalrearrangementOfa-andy-methallyldiethyphOSPhorothionaesinrelallontotheregioselectivityObserVedinthePalladium(O)catalySisl'].InourPreviousStUdy,Hg(II)catalghcandthermalffoono-ffoolorearrangmentOfcrPrOPargylcreqlp…     

A New and Practical Procedure for the Preparation of the Glucohexatose Phytoalexin Elicitor

The phytoalexin elicitor β-(1→3)-branched β-( 1→6)-linked glucohexatose has been regio- and stereospecifically synthesized by coupling of the 3, 6-branched gluco-trisaccharide Schmidt reagent 10 with a mixture of multiol 3,6-branched gluco-trisaccharides 13 which consists of free 5,6‘-OH trisaccharide, free 5,2‘ ,6‘-OH trisaccharide, free 5,3‘ ,6‘-OH trisaccharide and so on. The compounds 10 and 13 were prepared from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose , 2, 3, 4, 6-tetra-O-ben-zoyi-a-D-glucopyranosyl trichioroacetimldate, and 2,3,4, 6-tetra-O-acetyl-α-D-glucopyranosyl trichloreacetimidate through regio- and stereoselective manners.     

A Mild and Efficient Procedure for the Preparation of Chromone-2-carboxylates

Chromone-2-carboxylates are widely used for the pharmacological activity of several of its derivatives1. The general synthesis of such chromone derivates includes two steps (Scheme 1): a Claison condensation of dialkyl oxalate with 2-hydroxyacetophenones to achieve alkyl 3-(2-hydroxyphenyl)-3-oxopropanoates in the presence of NaH, NaOEt, or NaOMe; cyclodehydration of the alkyl 3-(2-hydroxyaryl)-3-oxopropanoates to obtain chromones under acid condition. The total yield of the two steps is q…     

Effect of Ni Loading on the Catalytic Properties of Molybdenum Oxides for the Isomerization of Heptane

The catalytic properties of MoOx and incorporation Ni onto the MoOx for the isomerization of heptane have been investigated under atmospheric pressure at different conditions such as different flow rate of H2,different reaction temperature tec. Compared with MoOx, the Ni addition to the MoOx markedly improved the isomerization activity of heptane by improving the reducibility of MoO3 and activation of H2 in reaction.     

Observations on the Preparation of β-Lactose Octaacetate

Attempts to substantially increase the relative proportion of β-lactose octaacetate in products of acetylation of α-lactose monohydrate using various acetylation protocols failed. Nevertheless, the revised protocol for isolation and crystallization, based on the classical work by Hudson and Johnson, rendered preparation of β-lactose octaacetate less labor intensive. It is proposed that the melting point and [α]_D value are not reliable criteria of purity of β-lactose octaacetate, which can be confidently determined by 1H NMR spectroscopy.     

Simple and Efficient Method for the Synthesis of δ‐Chloroesters from Tetrahydrofuran and Acyl Chlorides in the Presence of Catalytic Iodine

Acyl chlorides and dry tetrahydrofuran (THF) in the presence of catalytic amounts of iodine at 25°C give δ‐chloroesters in excellent yields.     

Effect of magnesium cations on the activity and stability of β-galactosidases

It was shown that the presence of magnesium cations in the reaction mixture increases, approximately twofold, the activity of bacterial Escherichia coli and yeast Kluyveromyces lactis β-galactosidases but does not affect the activity of bovine liver and fungous Penicillium canescens β-galactosidases. The catalytic constants for E. coli and yeast K. lactis β-galactosidases in the presence of 0.01 M and in the absence of Mg²⁺ cations were determined (490 and 220 s^?1 and 59.8 and 37.4 s^?1, respectively). It was shown that the Michaelis constants for these two enzymes are higher in the presence of Mg²⁺ cations, that the thermal stability of E. coli and K. Lactis β-galactosidases is higher in the presence of 0.01 M Mg²⁺, and that the effective rate constants of thermal inactivation of the enzymes are two-to eightfold lower, depending on conditions, in the presence of Mg²⁺ cations. The maximum stabilizing effect of magnesium cations was observed at weak alkaline pH values (7.5–8.5).     

Effect of Alkali Treatment on the Structure and Catalytic Properties of ZSM-5 Zeolite

Catalytic properties of ZSM-5 zeolite samples pretreated with NaOH solution have been investigated. The samples are characterized by XRD, SEM, chemical analysis, and N2 adsorption.The results indicate that mesopores are created in ZSM-5 crystals under alkali treatment without change the microporous structure and acidic strength of the zeolite, but the crystallinity is greatly decreased under severe treatment. IR indicates that the concentration of silanol is greatly enriched by alkali treatment. The etherification activities of ZSM-5 zeolites are greatly increased byalkali-treatment. The noticeably improved catalytic activity of treated samples is ascribed to the formation of mesopores and greatly enriched silanol group.     

Efficient Procedure for the Preparation of Oligomer-Free N α -Fmoc Amino Acids

A two-step method is presented for the peptide-free, high-purity, and high-yield synthesis of N^α-Fmoc amino acids. The first step involves the preparation of stable dicyclohexylammonium–amino acid ionic adduct in acetone. Subsequently, the ionic adducts, on reaction with Fmoc-Nosu under mild alkaline conditions, give dipeptide-free N^α-Fmoc amino acids. The positive charge of the dicyclohexylammonium counterion in the ionic salt has a longer radius, moderating the nucleophilicity of the carboxylate ion of the amino acid and preventing by-products by arresting the formation of mixed anhydrides, the precursors of oligopeptide impurities.     

An Improved Method for the Syntheses of β-Substituted Cyclohexenones

An improved method for the preparation of β-substituted cyclohexenones is reported. Conditions were defined to effectuate the key desulfonylation-deketalization step in a mild manner. Several cyclohexenones bearing acid and/or base sensitive β-substituents were prepared by the modified method in moderate to good yields.     

Effect of substituents on the solubility and the distribution of alkyl-substituted β-diketone iron chelates

The solubilities and the distributions of nine alkyl-substituted β-diketone iron chelates were measured in a number of common organic solvents, in order to establish the effect of substituents. In synthesis of iron chelates, acetylacetone, di-isobutyrylmethane and di-pivaloylmethane chelates were available with red-orange solid, while other chelates were red-orange oil. Using the solubilities and the respective molar volumes of these solid chelates, the solubility parameter values (δ_M) were calculated. The constancy of the calculated values was taken as evidence of the adequacy of the regular solution concept for explaining the observed solubility trends in the solvents studied. The molar volumes of iron chelates were nearly 1.5 times those of corresponding copper chelates and the solubility parameter values of the former were about the same as those of the latter. In the extraction of iron chelates, the extracted species were identified to be FeA₃ (A: β-diketone anion). The extraction constants (K_ex) of iron chelates does not depend on the nature of organic solvents. The distribution coefficients (P_Fe) of iron chelates increase regularly with the increase in the number of additional carbon atoms of the alkyl chain in the chelate molecule. The relationship between the solubilities or the distribution ratios of iron chelates and those of corresponding copper chelates were discussed.     

Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.     

A Convenient Procedure for the Synthesis of 6-O-Mono-Phosphate β-Cyclodextrins

Abstract

The synthesis of β-cyclodextrin derivatives bearing one phosphate group on the primary rim is reported. These compounds were prepared in good to excellent yields, by reacting β-cyclodextrin with dialkyl chlorophosphates in the presence of 4-dimethyl amino pyridine (DMAP) catalyst and dimethylformamide (DMF) as solvent. The methodology described is highly selective and the purification of the title compounds is simple, because difficulties due to phosphate regioisomers mixture are avoided.     

Comparative Study on the Effect of NaBr on the Interaction Between Alkyltrimethylammonium Bromide and β-Cyclodextrin

The effect of NaBr on the interaction between alkyltrimethylammonium bromide (CnTAB (n = 14 for TTAB and 16 for CTAB)) and ß-CD was studied by surface tension method. The first decrease in the γ_cmc of TTAB/ß-CD in the presence of NaBr mainly due to the elongated effective chain length of the hydrophobic part of the TTAB/ß-CD complexes; while the increase in the γ_cmc of both of the TTAB/ß-CD and CTAB/ß-CD in the presence of NaBr could be attributed to the close pack of CnTAB at the air/water interface.     

Preparation of Ultrafine Pigment Dispersion and Effect on ξ‐Potentials

The waterborne ultrafine pigment C.I.P.B15∶1 dispersion was prepared with copolymer by the phase separation method. The shape and size distribution of ultrafine pigment particles were investigated, and the effects of pH value, ion intensity, and alcohols on ξ‐potentials were analyzed. The results showed that stick‐shaped particles with narrow distribution were obtained, ξ‐potentials obviously increased with increasing of pH value in the range of 5–9, and when the pH value was at 8–9, the ξ‐potential reached its maximum. Moreover ξ‐potentials decreased with increasing ion intensity, decreased by adding the alcohols into the dispersion, and also decreased with increase in the dosage of Triton TX‐10.     

New Approaches for Preparation of β-CDP-PAN and its Characterization

A new type of Electrorheological materials made of an inclusive complex, which was synthesized by the means of molecular self-assembly, show a stronger electrorheological effec than that ofβ-cyclodextrin cross-linking polymer (β-CDP). Three approaches, named liquid-phase, solid-phase and liquid-solid-phase method, are respectively proposed to prepareβ-CDP-PAN, and show that both of the solid-phase and liquid-solid-phase methods are simple and convenient. The inclusion complex was characterized by the fluorescence spectrophotometer, IR and XRD confirming that the naphthalene ring of 1-(2-pyridlazo)-2-naphthol (PAN) was included in the glycopyranose unit ofβ-CDP.