Solid catalysts for the production of fine chemicals: the use of natural phosphate alone and doped base catalysts for the synthesis of unsaturated arylsulfones

The inexpensive natural phosphate, both alone and doped with potassium fluoride, is a new basic catalyst for the synthesis of α,β-unsaturated arylsulfones. Activation by water and benzyltriethylammonium chloride has also been investigated. When using an ammonium salt, natural phosphate doped with potassium fluoride is an excellent solid support for the synthesis of α,β-unsaturated arylsulfones, leading to excellent yields in a few minutes.     

One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles Directly from Nitrile and Hydroxylamine Hydrochloride Under Solvent-Free Conditions Using Potassium Fluoride as Catalyst and Solid Support

A one-pot synthesis of 3,5-disubstituted 1,2,4-oxadiazoles with two identical substituents directly from the reaction of nitriles and hydroxylamine hydrochloride in the presence of potassium fluoride as catalyst and solid support under solvent-free condition is described. Moreover, the formation of products has been discussed, and a plausible mechanism has been presented. Simplicity of the process, workup in aqueous media, and excellent yields are some advantages of this method.     

Direct aqueous injection gas chromatographic analysis of polar compounds using sorbents containing potassium fluoride dihydrate

Summary For direct aqueous injection gas-chromatographic analysis of polar compounds present in aqueous solutions sorbents containing conventional stationary phases and potassium fluoride crystal hydrate are proposed. On such sorbents polar compounds elute with narrow symmetrical zones under gentle chromatographic conditions. In such sorbents KF.2H₂O mainly deactivates the surface of the solid support. The polarity of these sorbents is compared with the polarity of molten potassium fluoride dihydrate and conventional stationary phases.     

Polymer-supported synthesis of regioregular head-to-tail-coupled Oligo(3-arylthiophene)s utilizing a traceless silyl linker

The solid-phase synthesis of regioregular head-to-tail-coupled oligo(3-arylthiophene)s has been achieved in high yield and purity by using a traceless silyl ether linkage. In the first step, the solution-phase synthesis of this class of conjugated oligomers was investigated. Benzyl alcohol was chosen to serve as a mimic for the anchoring group of the hydroxymethyl-substituted polystyrene matrix. The development of a novel regioselective iodination process for silyl-protected thiophenes faciliates the successful application of the solution-phase protocol to the solid phase. Satisfactory loading was obtained by reaction of chlorosilyl-functionalized 3-arylthiophene with hydroxymethyl polystyrene in the presence of imidazole. The suitability of the following iterative halogenation and Suzuki cross-coupling sequence is illustrated by the preparation of a quater(3-arylthiophene), the first regioregular head-to-tail-coupled oligothiophene that is synthesized on solid support. Removal of the conjugated oligomers from the solid support could be effectively achieved by treatment with tetrabutylammonium fluoride.     

Novelties of solid-liquid phase transfer catalysed synthesis of p-toluenesulfonyl fluoride from p-toluenesulfonyl chloride

Organic sulfonyl fluorides are of interest owing to their insecticidal, germicidal and enzyme inhibitory properties. In the current work, synthesis of p-toluenesufonyl fluoride was accomplished by reacting p-toluenesulfonyl chloride with solid potassium fluoride using PEG-400 as a catalyst under solid-liquid phase transfer catalysis (S-L PTC) at 30 °C. p-Toluenesulfonyl fluoride is used as peroxygen bleach activator. It also finds use in the treatment of Alzheimer's disease. The mechanism is based on homogeneous solubilization of solid. PEG forms a complex with metal cation which associates with the nucleophile and it participates in SN₂ type reactions. The reaction is intrinsically kinetically controlled. A complete theoretical analysis is done to determine both the rate constant and equilibrium constant from the same set of data. The activation energy and Gibbs free energy are also calculated.     

Novelties of solid-liquid phase transfer catalysed synthesis of p-toluenesulfonyl fluoride from p-toluenesulfonyl chloride

Organic sulfonyl fluorides are of interest owing to their insecticidal, germicidal and enzyme inhibitory properties. In the current work synthesis of p-toluenesufonyl fluoride was accomplished by reacting p-toluenesulfonyl chloride with solid potassium fluoride using PEG-400 as a catalyst under solid-liquid phase transfer catalysis (S-L PTC) at 30 °C. p-Toulenesulfonyl fluoride is used as peroxygen bleach activator. It also finds use in the treatment of Alzheimer's disease. The mechanism is based on homogeneous solubilization of solid. PEG forms a complex with metal cation which associates with the nucleophile and it participates in S_N2 type reaction. The reaction is intrinsically kinetically controlled. A complete theoretical analysis is done to determine both the rate constant and equilibrium constant from the same set of data. The activation energy and Gibbs free energy are also calculated.     

Cocatalysis in phase-transfer catalyzed fluorination of alkyl halides and sulfonates

Phase-transfer catalyzed (PTC) fluorination of alkyl halides and sulfonates with solid KF proceeds efficiently when cocatalyst triphenyltin fluoride is used. The cocatalytic action of the tin compound consists in continuous formation of difluorotriphenylstannate anion that as the tetraalkyloammonium salt enter the solution where it reacts with alkyl halides to produce alkyl fluorides. The cocatalytic system was used to synthesis of 1,1-difluoroalkanes in two steps from aldehydes. A new kind of PTC was elaborated in which Ph₃SnF acts as phase transfer catalyst via continuous formation of potassium salts of diflurotriphenylstannate anions soluble in dipolar aprotic solvents. A new, simple and general method of synthesis of tetraalkylammonium and potassium salts of difluorotriorgano-tin, silicon and germanium anions is reported.     

Solid-phase synthesis of linear ureas tethered to hydantoins and thiohydantoins

An efficient method for the solid-phase synthesis of hydantoins and thiohydantoins tethered to ureas, starting from a resin-bound amino acid, is presented. Following reduction of the amide with borane-THF, a second amino acid was selectively coupled to the primary amine followed by treatment of the secondary amine by an isocyanate to generate the corresponding urea. Hydantoin and thiohydantoin formation was achieved through the use of carbonyldiimidazole and thiocarbonyldiimidazole, respectively. Cleavage from the solid support using hydrogen fluoride, followed by extraction and lyophilization, provided the desired urea-linked heterocyclic compounds in good yield and high purity.     

An environmentally benign and practical synthesis of sugar orthoesters promoted by potassium fluoride

An extremely practical method for synthesis of sugar orthoesters has been developed without using any organic amines or heavy metals as additives. Various sugar orthoesters were prepared in good yields by the reaction of an acylated glycosyl bromide and an alcohol in the presence of potassium fluoride.     

Fluoride-conversion synthesis of homogeneous actinide oxide solid solutions

The synthesis of (U,Th)O(2) solid solutions at a relatively low temperature of 1100 °C using a new technique is described. First, separate actinide oxides were reacted with ammonium hydrogen fluoride to form ammonium actinide fluorides at room temperature. Subsequently, this fluoride was converted to an actinide oxide solid solution using a two-phase reaction process, which involved heating of the fluoride first at 610 °C in static air followed by heating at 1100 °C in flowing argon. Oxide solid solutions of UO(2) and ThO(2) were synthesized for a ThO(2) content from 10 to 90 wt %. Microscopic investigation showed that the (U,Th)O(2) solid solutions synthesized using this method had high crystallinity and homogeneity up to nanoscale.     

Cascade iodination-fluorination synthesis of 2-fluorothiophene and 5-fluoro-2-thienyliodonium salts

The first synthesis of fluorine-containing 2-thienyliodonium salts was accomplished using cascade iodination-fluorination. According to this methodology, thiophene is first converted to bis(2-thienyl)iodonium hexafluorophosphate using an electrophilic iodination reaction. Upon heating with potassium fluoride, this salt undergoes regioselective fluorination producing 2-fluorothiophene. 2-Fluorothiophene is then iodinated again to yield fluorothienyliodonium salts.     

香豆素合成工艺的改进

香豆素是一种用途广泛的香料,虽然已有多种合成方法,但国内仍采用以水杨醛为原料的路线(产率为60%左右),提高产率是改进其合成工艺的关键。我们曾以氟化钠代替乙酸钠作催化剂,以水杨醛和乙酐为原料合成了香豆素,提高了产率。本文又采用两     

Synthesis of 2'-C-beta-fluoromethyluridine

[reaction: see text] 2'-C-beta-Fluoromethyluridine (17) represents both a potentially important biological agent and a tool for biochemical analysis. Here we describe the first synthesis of this compound starting from uridine. The key steps include protection of the uracil base with methoxyethoxymethyl (MEM) chloride, conversion to the corresponding 2'-C-alpha-epoxide, and regioselective opening of the oxirane ring with potassium fluoride/hydrogen fluoride. Subsequent acetylation of the 3'- and 5'-hydroxyl groups enables MEM removal using B-bromocatecholborane. Deacetylation generates the parent nucleoside, 2'-C-beta-flurormethyluridine.     

Nuclear momentum distribution in solid and liquid HF from ab initio calculation

A calculation of nuclear momentum distribution of liquid and solid hydrogen fluoride was performed. In both systems, density functional theory generalized gradient approximation functional of Perdew, Burke, and Ernzerhof was used for the calculation: for liquid hydrogen fluoride, using an atom centered basis set for an isolated molecule with optimized geometry, and for solid hydrogen fluoride using plane-wave basis sets on optimized orthorhombic crystal cell. For liquid hydrogen fluoride, a semiclassical approach was adopted with the vibrational contribution to momentum distribution obtained from the density functional theory calculation and translational and rotational contributions calculated classically. Nuclear momentum distribution in the solid hydrogen fluoride was calculated entirely quantum mechanically using phonon dispersion and vibrational density of states calculated in the framework of plane-wave density functional theory. Theoretical results were contrasted with recently obtained results of Compton (deep inelastic) neutron scattering on liquid and solid hydrogen fluoride. In case of liquid hydrogen fluoride, almost a perfect agreement between theory and experiment was achieved within the harmonic Born-Oppenheimer approximation. For the solid system under investigation, the harmonic approximation leads to small (4%) overestimation of the square root of the second moment indicating that neutron Compton scattering technique is sensitive to proton delocalization due to hydrogen bonding in solid hydrogen fluoride.     

Asymmetric addition of arylboronic acids to glyoxylate catalyzed by a ruthenium/Me-BIPAM complex

The enantioselective synthesis of α-hydroxy esters by ruthenium-catalyzed 1,2-addition of arylboronic acids to tert-butyl glyoxylate is described. The use of RuCl(2)(PPh(3))(3) with (R,R)-Me-BIPAM gave optically active mandelic acids of up to 99% ee. Addition of a fluoride salt such as potassium fluoride (KF) or caesium fluoride (CsF) was effective for achieving high enantioselectivities.     

The 2-(diphenylphosphino) ethyl group (DPPE) as a new carboxyl-protecting group in peptide chemistry

The use of the 2-(diphenylphosphino)ethyl group for carboxyl-protection of amino acids or peptides is described. This group is easily introduced by esterification using 2-(diphenylphosphino) ethanol in the presence of dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine. These Dppe esters are stable under the standard conditions for peptide synthesis. Deprotection is carried out under mild conditions by quaternisation using methyl iodide followed by a β-elimination induced by fluoride ion or potassium carbonate.     

The electrode behaviour of zinc in ternary alkaline electrolytes stabilized by silicate

The vapour pressure of alkaline solutions has been measured using a modified version of the Ramsay and Young method. The addition of potassium fluoride to 3 molar potassium hydroxide containing 0.15 molar potassium silicate lowers the vapour pressure to that of 8 molar potassium hydroxide. The ternary mixture of fluoride/hydroxide/silicate may be suitable for application in primary zinc/air cells, as the previously reported slurry region is still observed with this electrolyte. The limitations of this mixed electrolyte are discussed.     

Optimizing Permselectivity for Neutral Carrier Membrane Electrodes

Abstract

A new format: solvent, support and surface coating, has been discovered which greatly improves the response time and linearity of response of valinomycin-based potassium ion selective electrodes. With the new system completely Nernstian responses are obtained up to 0.1 M for aqueous potassium salt solutions of oil insoluble through slightly oil soluble anions (fluoride through perchlorate in the Hofmeister series), and nearly Nernstian responses are obtained for potassium salts having more oil soluble anions, including picrate. Electrodes using the new format have characteristic short response times (30 secs. for 90% steady state), long life-times and freedom from “memory effects”.     

New eco-friendly animal bone meal catalysts for preparation of chalcones and aza-michael adducts

ABSTRACT: Two efficient reactions were successfully carried out using Animal Bone Meal (ABM) and potassium fluoride or sodium nitrate doped ABMs as new heterogeneous catalysts under very mild conditions. After preparation and characterization of the catalysts, we first report their use in a simple and convenient synthesis of various chalcones by Claisen-Schmidt condensation and then in an aza-Michael addition involving several synthesized chalcones with aromatic amines. All the reactions were carried out at room temperature in methanol; the chalcone synthesis was also achieved in water environment under microwave irradiation. Doping ABM enhances the rate and yield at each reaction. Catalytic activities are discussed and the ability to re-use the ABM is demonstrated. RESULTS: For Claisen-Schmidt the use of ABM alone, yields never exceeded 17%. In each entry, KF/ABM and NaNO3/ABM (79-97%) gave higher yields than using ABM alone under thermic condition. Also the reaction proceeded under microwave irradiation in good yields (72-94% for KF/ABM and 81-97% for NaNO3/ABM) and high purity. For aza-Michael addition the use of ABM doped with KF or NaNO3 increased the catalytic activity remarkably. The very high yields could be noted (84-95% for KF/ABM and 81-94% for NaNO3/ABM). CONCLUSION: The present method is an efficient and selective procedure for the synthesis of chalcones anaaza-Michael adducts. The ABM and doped ABMs are a new, inexpensive and attractive solid supports which can contribute to the development of catalytic processes and reduced environmental problems.     

Efficient Synthesis of 1-(4′-Methylbenzoyl)- 3,3-Diethylthiourea Under Microwave Irradiation Using Potassium Fluoride on Alumina

1,1-diethylthiourea and 4-methylbenzoic acid were condensed to 1-(4′-methylbenzoyl)-3,3-diethylthiourea in open vessels under microwave irradiation using an unmodified domestic microwave oven. The synthesis was carried out in the presence of alumina impregnated with potassium fluoride and catalytic amounts of N,N-dimethylformamide. The yields are noticeably improved in comparison with classical methods.