Preparation of trifluoroethyl- and phenyl-protected sulfates using sulfuryl imidazolium salts

Sulfuryl imidazolium salts (SIS’s), a new class of sulfating agents, were prepared bearing the trifluoroethyl (TFE) and phenyl groups, two functionalities that have been used for the protection of sulfate monoesters, by subjecting the corresponding sulfonyl imidazoles with methyl triflate. In contrast, SIS’s bearing the electron donating neopentyl and isobutyl groups, two moieties that have also been used for the protection of sulfates, were found to be unstable and could not be isolated though SIS’s bearing electron donating aryl groups, such as a p-methoxyphenyl or p-thiomethylphenyl group were readily prepared and are stable compounds. In most instances, TFE-protected phenolic and carbohydrate sulfates were obtained in good yield by reaction of the corresponding SIS’s with steroids and carbohydrates. Phenyl-protected carbohydrates were also readily prepared using the corresponding SIS’s. Those SIS’s having a methyl group at the 2-position of the imidazole ring were, in general, superior sulfating agents to those, which lacked a methyl group at this position. The use of SIS’s to prepare TFE-protected sulfates represents a significant improvement of the previous reported procedure, which involved treating unprotected sulfates with trifluorodiazoethane. The TFE protecting group was removed from steroidal sulfates and secondary sulfates in carbohydrates in high yields using NaN₃ in warm DMF, conditions that are less vigorous than those previously reported for removing this group. Deprotection of TFE-protected 6-sulfated carbohydrates using NaN₃ in warm DMF proceeded in lower yields due to partial desulfation.     

The synthesis and reactions of β-substituted ethyl sulfates

The synthesis of β-substituted ethyl sulfates and their reactions with nucleophilic reagents has been studied. Amines, phenolates, carboxylates, amine oxides, carbanions, and thiophenolates reacted with ethylene sulfate in high yield, with short reaction times, and at low temperatures, to form β-substituted ethyl sulfates. The β-substituted ethyl sulfates were easily hydrolyzed and in some cases were converted into polymeric material.     

Do electrostatic interactions with positively charged active site groups tighten the transition state for enzymatic phosphoryl transfer?

The effect of electrostatic interactions on the transition-state character for enzymatic phosphoryl transfer has been a subject of much debate. In this work, we investigate the transition state for alkaline phosphatase (AP) using linear free-energy relationships (LFERs). We determined k(cat)/K(M) for a series of aryl sulfate ester monoanions to obtain the Br?nsted coefficient, beta(lg), and compared the value to that obtained previously for a series of aryl phosphorothioate ester dianion substrates. Despite the difference in substrate charge, the observed Br?nsted coefficients for AP-catalyzed aryl sulfate and aryl phosphorothioate hydrolysis (-0.76 +/- 0.14 and -0.77 +/- 0.10, respectively) are strikingly similar, with steric effects being responsible for the uncertainties in these values. Aryl sulfates and aryl phosphates react via similar loose transition states in solution. These observations suggest an apparent equivalency of the transition states for phosphorothioate and sulfate hydrolysis reactions at the AP active site and, thus, negligible effects of active site electrostatic interactions on charge distribution in the transition state.     

Sulfate additives generate robust and highly active palladium catalysts for the cyanation of aryl chlorides

The use of sulfate additives such as H₂SO₄ greatly increases the reactivity of palladium catalysts for the cyanation of aryl and heteroaryl chlorides and renders them more robust toward adventitious air. Using this method, a wide variety of aromatic and heteroaromatic nitriles were prepared in high yield.     

Palladium-phosphinous acid-catalyzed cross-coupling of aryl and acyl halides with aryl-, alkyl-, and vinylzinc reagents

Several palladium-phosphinous acids have been prepared and employed in cross-coupling reactions of aryl or acyl halides with aliphatic and aromatic organozinc reagents. The POPd7-catalyzed reaction of aryl halides, including electron-rich aryl chlorides, and arylzinc reagents was found to afford biaryls exhibiting alkoxy, alkylthio, amino, ketone, cyano, nitro, ester, and heteroaryl groups in 75-93% yield. Excellent results were obtained with sterically hindered substrates which gave di- and tri -ortho-substituted biaryls in up to 92% yield. Aryl halides also undergo POPd7-catalyzed aryl-vinyl and aryl-alkyl bond formation under mild conditions. Styrenes and alkylarenes were prepared in 79-93% yield from aryl halides and vinyl or alkylzinc reagents. The replacement of aryl halides by acyl halides provides access to ketones which were produced in up to 98% yield when POPd was used as catalyst. This approach overcomes the limited substrate scope, reduced regiocontrol, and low functional group tolerance of traditional Friedel-Crafts acylation methods.     

Metal sulfates-catalyzed butanolysis of cellulose: butyl levulinate production and optimization

Direct production of butyl levulinate (BL) by butanolysis of cellulose was carried out using single or combined metal sulfates catalysts. The synergetic enhancement of the ferric sulfate and aluminum sulfate can improve the conversion of cellulose to BL. Moreover, the butanolysis of cellulose was optimized by using response surface methodology. Under the optimum conditions of 194 °C, catalyst concentration 10.0 g/L and reaction time 3 h, the average cellulose conversion of 100% and BL yield of 40.3% were obtained. In addition, the analysis of liquid products and the characterization of catalyst were performed, and the reusability experiments showed that the metal sulfates can be easily recycled and be reused more than five times with high activity in the butanolysis process. This study provided an economical and feasible method for bio-based BL production from cellulose.     

A concise synthesis of (+/-)-cacalol

A simple synthesis of the natural product cacalol has been developed that proceeds in seven steps and 21-25% overall yield. Ortho-lithiation of 4-methylanisole and alkylation with 5-iodo-1-pentene, followed by intramolecular Friedel-Crafts alkylation, gave 5-methoxy-1,8-dimethyltetralin. This compound was then formylated in the 6-position. Baeyer-Villiger oxidation and hydrolysis of the resulting formate gave 6-hydroxy-5-methoxy-1,8-dimethyltetralin. Alkylation of the phenolic hydroxyl group with chloroacetone followed by cyclodehydration gave cacalol methyl ether. Deprotection of this aryl methyl ether yielded cacalol.     

Photophysical studies of uranyl complexes: VIII. Luminescence spectra of UO2SO4 · 312H2O and two polymorphs of bis(urea) uranyl sulfate

The photoluminescence spectra of hydrated and anhydrous uranyl sulfates have been studied under conditions of high resolution at cryogenic temperatures. All uranyl sulfate systems were found to yield nonequivalent spectra: the energies for the electronic and vibronic origins were found to vary with the system, and certain uranyl vibrational frequencies exhibited a dependence on environment. These differences must reflect the various ways in which the uranyl centers are linked by the bridging sulfate groups, as this linking is the main difference between the various structures.     

Microwave-mediated reductive amination-cyclization of 4-aryl-4-oxobutanoates: Facile synthesis of 3-methylidene-5-phenyl-2,3-dihydropyrrolidones

Microwave-mediated three-component condensation of 4-aryl-4-oxobutanoates with ammonium formate furnishes 3-methylidene-5-phenyl-2,3-dihydropyrrolidones in good yield within 2 min. The pyrrolidone products were characterized on the basis of spectral data and X-ray crystal structure analysis. The reaction is found to be general and a variation in the ester and aryl moieties is possible. However, when alkylammonium formate is used only amide products are formed     

Efficient synthesis of triarylmethanes via bisarylation of aryl aldehydes with arenes catalyzed by silica gel-supported sodium hydrogen sulfate

An efficient synthesis of triarylmethanes has been developed via bisarylation of aryl aldehydes with arenes catalyzed by silica gel-supported sodium hydrogen sulfate in a solvent-free system. The new method features high yield, mild reaction conditions, and environmental friendliness.     

Detection of chondroitin sulfate-binding proteins on the membrane

Chondroitin sulfate is a ubiquitous component of proteoglycans that is present both in the extracellular matrix and at the cell surface of various tissues. Until recently, chondroitin sulfate has attracted less attention than heparan sulfate and dermatan sulfate, owing to the limited number of known chondroitin sulfate-binding proteins. To determine the biological function of chondroitin sulfate, biotinylated probes were prepared and used to search for binding proteins. Chondroitin sulfates A, C, D, and E were biotinylated through either the uronic acid or the residual core peptide. Lysates from mouse Lewis lung carcinoma (3LL) cells were blotted onto a nitrocellulose membrane after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the membrane was treated with the biotinylated chondroitin sulfates. Among the chondroitin sulfate variants, the E type showed the most intense bands upon visualization of the membrane with avidin-conjugated alkaline phosphatase and the appropriate substrates. The binding of chondroitin sulfate E to proteins in the cell lysate was not affected by the A, C or D variants but was reduced by treatment with dermatan sulfate. Lysates from 3LL cells were also treated with biotinylated chondroitin sulfate E and, after two-dimensional (2-D) electrophoresis and blotting, several chondroitin sulfate E-binding proteins including lamins and heterogeneous nuclear ribonucleoproteins were identified by mass spectrometry.     

Hydrogenation of azides over copper nanoparticle surface using ammonium formate in water

Aryl azides undergo clean reduction by copper nanoparticles and ammonium formate in water. The surface hydrogen on copper nanoparticles is considered to be the active reducing species. A variety of functionalized aryl azides and aryl sulfonyl azides are reduced by this procedure to the corresponding amines with excellent chemoselectivity in high yields.     

Facile solid phase synthesis of 1,2-disubstituted-6-nitro-1,4-dihydroquinazolines using a tetrafunctional scaffold

Solid phase synthesis of 1, 2-disubstituted-6-nitro-1,4-dihydroquinazolines is described. The new tetrafunctional scaffold N-Alloc-3-amino-3-(2-fluoro-5-nitrophenyl)propionic acid was prepared by nitration of 3-amino-3-(2-fluorophenyl)propionic acid. The scaffold was anchored to Rink resin via its carboxylic group and treated with primary amines to displace the arylfluorine followed by cyclization with aryl isothiocyanates in the presence of DIC upon Alloc deprotection to afford 1,2-disubstituted-6-nitro-1,4-dihydroquinazolines in high yield.     

微波炉加热法合成3-芳基-1, 2, 4-三唑啉-5-硫酮

本文报道了微波炉加热法合成3-芳基-1, 2, 4-三唑啉-5-硫酮,研究了反应时间, 溶液用量, 微波功率及芳基对反应产物收率的影响。     

The studies of the effect of sulfates added as chromium(VI) reducers in portland cement

The calorimetric measurements were applied in testing the effect of some sulfates, used as Cr(VI) reducers in cement, as setting and hardening modifiers. The iron(II) sulfate is most commonly added as Cr reducer to cement on grinding. This was taken as a reference in the studies of the other potential chromium reducers, such as tin(II) and manganese(II) sulfates on cement hydration. The high percentage of admixtures was reduced steadily from very high overdosage—to find the possible effect of non-homogeneity resulted from the hygroscopic character of compounds used and to detect the possible products which can be formed—to relatively small quantity, as used in practice. The progress of cement hydration was investigated by calorimetry and chemical shrinkage measurements. The rheological properties of cement paste admixtured with iron, tin, and manganese sulfates were investigated, as well as the phase composition of hydrated pastes was studies by XRD. The compressive strength of the small paste cylinders was measured. Finally, the hydrated samples were subjected to the SEM observations. The tin sulfate showed the strongest retarding action as it was proved by calorimetry and chemical shrinkage data, as well as by strength and rheological measurements; however, at small quantities, this compound has a positive impact on setting and hardening. The detrimental effect of overdosed Mn and Fe sulfates due first of all to the formation of higher amount of ettringite at very early age was found. This can be proved additionally by the change of rheological parameters—higher yield stress and viscosity.     

无溶剂条件下离子液体催化香豆素衍生物的绿色合成(英文)

Brnsted acidic ionic liquids, namely 2-pyrrolidonium hydrogen sulfate, N-methyl-2-pyrrolidonium hydrogen sulfate, N-methyl-2-pyrrolidonium dihydrogen phosphate, (4-sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulfate, and triphenyl(propyl-3-sulfonyl)phosphonium toluenesulfonate, catalyzed efficient Pechmann condensation of phloroglucinol with β-keto ethyl/ methyl esters. 5,7-Dihydroxy-4-methylcoumarin and 5,7-dihydroxy-4-phenylcoumarin were prepared in good to excellent yields under mild, ambient, and solvent-free conditions. Pyrano[2,3-h] coumarins were then prepared by one-pot three-component reactions of 5,7-dihydroxy-4-subsituted coumarin, malononitrile, and aldehydes in the presence of catalytic amounts of Br nsted basic ionic liquids, namely 2-hydroxyethylammonium formate, 3-hydroxypropanaminium acetate, 1-butyl-3-methylimidazolium hydroxide, pyrrolidinium formate, and pyrrolidinium acetate, under thermal solvent-free conditions. The catalysts are environmentally benign and can be easily prepared, stored, and recovered without significant loss of activity.     

A Multicatalytic Approach to the Hydroaminomethylation of α‐Olefins

We report an approach to conducting the hydroaminomethylation of diverse α‐olefins with a wide range of alkyl, aryl, and heteroarylamines at relatively low temperatures (70–80 °C) and pressures (1.0–3.4 bar) of synthesis gas. This approach is based on simultaneously using two distinct catalysts that are mutually compatible. The hydroformylation step is catalyzed by a rhodium diphosphine complex, and the reductive amination step, which is conducted as a transfer hydrogenation with aqueous, buffered sodium formate as the reducing agent, is catalyzed by a cyclometallated iridium complex. By adjusting the ratio of CO to H₂, we conducted the reaction at one atmosphere of gas with little change in yield. A diverse array of olefins and amines, including hetreroarylamines that do not react under more conventional conditions with a single catalyst, underwent hydroaminomethylation with this new system, and the pharmaceutical ibutilide was prepared in higher yield and under milder conditions than with a single catalyst.     

Semi-synthetic polysaccharide sulfates as anticoagulant coatings for PET, 1--cellulose sulfate

In the present study, blood-compatible PET surfaces were prepared by coating with anticoagulant cellulose sulfates that were synthesized homogeneously in ionic liquids. The adsorption behavior of polysaccharides on PET films was investigated using QCM-D. It was demonstrated that pre-coating with different amino-group-containing polysaccharides improves the affinity toward cellulose sulfate. Moreover, the effect of different degrees of sulfation on the adsorption process was evaluated. Based on these results, several layer-by-layer coated PET foils were prepared that showed significantly improved blood compatibility compared to the initial untreated material.     

Perfluorocyclohexenyl aryl ether polymers via polycondensation of decafluorocyclohexene with bisphenols

A novel class of semifluorinated perfluorocyclohexenyl (PFCH) aryl ether homo/copolymers was successfully synthesized with high yield through the step‐growth polymerization of commercially available bisphenols and decafluorocyclohexene in the presence of a triethylamine base. The synthesized polymers exhibit variable thermal properties depending on the functional spacer group (R). PFCH aryl ether copolymers with random and alternating architectures were also prepared from versatile bis‐perfluorocyclohexenyl aryl ether monomers. The PFCH polymers show high thermal stabilities with a 5% decomposition temperature ranging from 359 to 444 °C in air and nitrogen atmosphere. These semifluorinated PFCH aromatic ether polymers contain intact enchained PFCH olefin moieties, making further reactions such as crosslinking and application specific functionalization possible. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 232–238     

Aryl trifluoromethyl acetylenes

A wide variety of aryl trifluoromethyl acetylenes may be prepared in high yield by allowing CF₃CCZnCl, generated from CF₃CCH, to react with aryl iodides a catalytic amount of tetrakis(triphenylphosphine)-palladium.