Iron‐catalyzed cross‐coupling reaction: Heterogeneous palladium and copper‐free Heck and Sonogashira cross‐coupling reactions catalyzed by a reusable Fe(III) complex

An interesting silica‐supported iron catalyst was successfully prepared and demonstrated as an efficient heterogeneous catalyst for cross‐coupling reactions of aryl halides. The as‐prepared nanocatalyst was well characterized and found to be highly efficient in Heck reaction under mild and sustainable conditions (water as solvent at 80 °C in short reaction time). Furthermore, the obtained catalyst was used as an efficient, inexpensive and green heterogeneous catalyst for Sonogashira cross‐coupling reactions of various aryl iodides and provided the corresponding products with moderate to good yields. This phosphine, copper and palladium‐free catalyst was simply recovered from the reaction mixture and recycled five times without substantial decrease in its catalytic activity.     

An efficient and facile one-pot synthesis of structurally unique 2,4,6-tris(arylchalcogeno)-1,3,5-triazine and 1,3,5-tris(arylchalcogeno)-2,4,6-trimethylbenzene

An efficient one-pot synthesis of a novel class of 2,4,6-tris(arylchalcogeno)-1,3,5-triazine (sulfur, selenium and tellurium) and 1,3,5-tris(arylchalcogeno)-2,4,6-trimethylbenzene (sulfur and selenium)-containing ligands has been developed based on the reaction of 2,4,6-trichloro-1,3,5-triazine and 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene with the corresponding arylchalcogenide anions generated in aqueous tetrahydrofuran.     

Synthesis of (arylselanyl)- and (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines via a copper-catalyzed multicomponent reaction

An efficient copper-catalyzed multicomponent reaction was developed for the synthesis of (arylselanyl)- or (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines. The products were obtained in moderate to excellent yields via the reaction of o-phenylenediamine, 2-azidobenzaldehyde and different arylchalcogenyl alkynes using catalytic copper iodide in 1,4-dioxane at 100?°C. The reactions tolerated a range of substituents on the arylchalcogenyl alkynes and proved to be an efficient methodology for the combinatorial synthesis of new selenium or sulfur-containing triazonine derivatives.     

Nano tetraimine Pd(0) complex as an efficient catalyst for phosphine‐free Suzuki reaction in water and copper‐free Sonogashira reaction under aerobic conditions

A nano tetraimine Pd(0) complex catalyst was successfully used as an efficient heterogeneous catalyst for the phosphine‐free palladium‐catalysed Suzuki coupling reaction in water at 80 °C. This nano tetraimine Pd(0) complex was also used for copper‐free Sonogashira reaction in dimethylformamide at 100 °C. The catalyst was easily recovered from the reaction mixture by centrifugation and reused for at least six cycles without any significant loss in its catalytic activity. Analysis of the reaction mixture using inductively coupled plasma analysis showed that leaching of palladium from the catalyst was negligible. The reactions can be performed efficiently for aryl iodides, bromides and also chlorides. Copyright © 2016 John Wiley & Sons, Ltd.     

Flow-injection simultaneous determination of selenium(IV) and selenium(IV + VI) using photooxidative coupling of p-hydrazinobensenesulfonic acid with N-(1-naphthyl)ethylenediamine

A flow-injection spectrophotometric method has been developed for the simultaneous determination of selenium(IV) and (IV + VI) at nanogram per milliliter levels. It is based on the catalytic effect of selenium(IV) on the photooxidative coupling of p-hydrazinobenzenesulfonic acid (HBS) with N-(1-naphthyl)ethylenediamine (NED) to form an azo dye (λ_max = 538 nm). In this reaction, bromide acted as an activator for the catalysis of selenium(IV) and an reducer for selenium(VI) to selenium(IV) in an acidic medium which allowed the determination of selenium(IV + VI). A sample solution, being split by Y-piece into two portions, passed through the low-temperature coil (4 m, 25 °C) and the high-temperature coil (20 m, 100 °C). By monitoring the absorbance of the dye produced in the two portions, selenium(IV) and (IV + VI) in the range of 0.2–6 ng ml⁻¹ were determined simultaneously. The relative standard deviations for 3 ng ml⁻¹ selenium(IV) and (VI) (n = 10) were 1.2 and 1.3%, respectively. There were few interfering ions in the selenium determination. The proposed method was applied to the determination of selenium(IV) and (VI) in natural water samples.     

Solvothermal synthesis and structure of a new selenium-rich selenophosphate K(3)PSe(4).2Se(6)

The compound K(3)PSe(4).2Se(6) was synthesized at 110 degrees C via solventothermal techniques from binary starting materials and Se in acetonitrile. The compound crystallizes in the space group Fd macro 3 of the cubic system with eight formula units in a cell with a dimension of a = 16.415(2) A at T = 193 K. The structure contains an unusual intermixing of ionic and uncharged species. The selenophosphate tetrahedral trianions PSe(4)(3-) are surrounded by potassium cations; other potassium cations in the structure are coordinated to 12 selenium atoms from four Se(6) rings in a tetrahedral arrangement. There are no short contacts between adjacent selenium rings. Heating the same reaction mixture to 160 degrees C results in the formation of only needles of trigonal selenium.     

Novel asymmetric michael addition of alpha-cyanopropionates to acrolein by the use of a bis(oxazolinyl)phenylstannane-derived rhodium(III) complex as a chiral Lewis acid catalyst

The rhodium complex prepared in situ by simply mixing [[RhCl(c-octene)2]2] and [(Phebox)SnMe3] (1) (Phebox = 2,6-bis(oxazolinyl)phenyl) was found to serve as an efficient catalyst for the asymmetric Michael addition of alpha-cyanopropionates (4) to acrolein under mild and neutral conditions. In the present catalytic system, both the temperature of catalyst preparation and the order of the addition of the substrates were very important for the catalytic efficiency and enantioselectivity. Detailed mechanistic studies of this catalytic system revealed that the [(Phebox)RhIII(SnMe3)Cl] complex (9), generated by oxidative addition of [[RhCl(c-octene)2]2] to 1, is an active catalyst and the turnover number (TON) of the present actual catalyst existing in a reaction mixture is greater than 10,000. The obtained (R) stereochemistry of the Michael adducts 5 can be explained by N-bonded enol intermediates C', which are formed by enolization of 4 bound to the Lewis acidic rhodium complex 9. We also found that the active catalyst 9 gradually decomposed in the presence of the remaining [[RhCl(c-octene)2]2] in the reaction mixture to form the catalytically nonactive [(Phebox)RhCl2] fragment A, whose structure was characterized by an X-ray crystallographic study after converting to the tBuNC complex 10.     

Oxidation of alcohols to aldehydes and ketones using selenium ionic liquid

A new type of ionic liquid supported selenium reagents were synthesized and found to be an excellent catalyst in the oxidation of alcohols to aldehydes and ketones in the presence of 30%H₂O₂.The predictable solubility of ionic liquids allows an easy separation of the oxidation products from the reaction mixture.Furthermore,the oxidation reaction can be carried out using an ionic liquid as the solvent,and the ionic liquid-supported selenium reagents can be recycled and used for four times with a little decrease in catalytic performance.     

Synthesis and catalytic properties of molybdenum(VI) complexes with tris(3,5-dimethyl-1-pyrazolyl)methane

The complex [MoO(2)Cl{HC(3,5-Me(2)pz)(3)}]BF(4) (1) (HC(3,5-Me(2)pz)(3) = tris(3,5-dimethyl-1-pyrazolyl)methane) has been prepared and examined as a catalyst for epoxidation of olefins at 55 °C using tert-butyl hydroperoxide (TBHP) as the oxidant. For reaction of cis-cyclooctene, epoxycyclooctane is obtained quantitatively within 5 h when water is rigorously excluded from the reaction mixture. Increasing amounts of water in the reaction mixture lead to lower activities (without affecting product selectivity) and transformation of 1 into the trioxidomolybdenum(VI) complex [{HC(3,5-Me(2)pz)(3)}MoO(3)] (4). Complex 4 was isolated as a microcrystalline solid by refluxing a suspension of 1 in water. The powder X-ray diffraction pattern of 4 can be indexed in the orthorhombic Pnma system, with a = 16.7349(5) ?, b = 13.6380(4) ?, and c = 7.8513(3) ?. Treatment of 1 in dichloromethane with excess TBHP led to isolation of the symmetrical [Mo(2)O(4)(μ(2)-O){HC(3,5-Me(2)pz)(3)}(2)](BF(4))(2) (2) and unsymmetrical [Mo(2)O(3)(O(2))(2)(μ(2)-O)(H(2)O){HC(3,5-Me(2)pz)(3)}] (3) oxido-bridged dimers, which were characterized by single-crystal X-ray diffraction. Complex 2 displays the well-known (Mo(2)O(5))(2+) bridging structure where each dioxidomolybdenum(VI) center is coordinated to three N atoms of the organic ligand and one μ(2)-bridging O atom. The unusual complex 3 comprises dioxido and oxidodiperoxo molybdenum(VI) centers linked by a μ(2)-bridging O atom, with the former center being coordinated to the tridentate N-ligand. The dinuclear complexes exhibit a similar catalytic performance to that found for mononuclear 1. For complexes 1 and 2 use of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate and N-butyl-3-methylpyridinium tetrafluoroborate as solvents allowed the complexes to be completely dissolved, and in each case the catalyst and IL could be recycled and reused without loss of activity.     

Interaction forces between a deformable air bubble and a spherical particle of tuneable hydrophobicity and surface charge in aqueous solutions

Unsupported nanosized MoS(2) and CoMo-sulfide catalysts were synthesized, and their catalytic performances for the deep hydrodesulfurization (HDS) of treated gas oil were investigated as compared with that of a CoMo/Al(2)O(3) catalyst. The HDS reactions were carried out in a batch autoclave reactor at 340 °C and 3 MPa H(2). The CoMo-sulfide catalyst shows the highest activity and can reduce the sulfur content to less than 10 ppm. The decrease in total sulfur content as a function of reaction time was found to follow pseudo-second order kinetics (empirical form). The change in the concentration of some individual representative sulfur-containing species in gas oil as a function of time was found to follow pseudo-first-order kinetics. However, the change in combined concentration of these species in the gas oil during HDS with the reaction time was found to corroborate pseudo-second-order kinetics. A kinetic model approach was proposed from which an estimation of the intrinsic kinetic data can be achieved. The model fitted the obtained data reasonably well, suggesting its potential for better assessment of the catalytic activity in the HDS of real feedstock. The study reveals that ranking of catalyst activities using model refractory sulfur-containing compounds does not necessarily imply a typical rank in case of investigating the real feedstocks.     

Palladium(II)-catalyzed transfer vinylation of protected monosaccharides

A method for the catalytic vinylation of protected monosaccharides bearing a single free hydroxyl function has been developed. Reaction of representative primary, secondary, and anomeric sugar hydroxyl functions with butyl vinyl ether as the reactant and solvent and (phen)Pd(OAc)(2) (phen = 1,10-phenanthroline ligand) as the catalyst gives the corresponding vinylated sugar products in 36-79% yield. The catalyst requires the presence of traces of oxygen in the reaction mixture to prevent decomposition to Pd(0).     

Cu(I)-catalyzed hetero-Diels-Alder reaction between Danishefsky-type siloxy dienes and ketones

A general catalytic method for the hetero-Diels-Alder reaction between Danishefsky-type siloxy dienes and ketones was developed. Optimum results were produced with a catalyst generated from CuOTf x (C6H6)1/2 and TBAT with Ph 3PO as the catalytic additive. This reaction was extended to an asymmetric variant, using a Cu(I)-Walphos catalyst.     

Silica iminopyridine-functionalized nanomaghemite enhances the oxygenation activity and durability of simple Co(II) salophen complex

A novel magnetically recoverable catalyst was produced by coordinative attachment of Co(II) salophen complex to silica iminopyridine (SIPy)-functionalized-γ-Fe₂O₃ magnetic nanoparticles (SMNP@SIPy/Co(II) salophen). The vibration spectra and compositional data provided sufficient evidences for the structural integrity of as-prepared organic–inorganic nanohybrid. The magnetic nanocatalyst proved to be an efficient and selective heterogeneous catalyst for oxidation of different benzylic alcohols and featured higher catalytic activity and stability than that of homogenous counterpart. A TOF of 151 h⁻¹ and TON of more than 322 were obtained for oxidation of 4-cholrobenzyl alcohol in this catalytic system. The supported catalyst could easily be recovered from the reaction mixture by an external magnetic field and reused for subsequent experiments with consistent catalytic activity.     

新型合成尿素用CO2原料气消氢催化剂的研究

介绍了新型合成尿素用CO₂原料气消氢催化剂的设计思路,研制出一种高活性强抗硫节能消氢催化剂.在催化活性和抗硫中毒性能方面优于已工业应用的催化剂,具有广阔的应用前景.     

VPO催化剂P/V比对丙烷晶格氧选择氧化制丙烯酸和乙酸的影响

丙烷选择氧化制取丙烯酸(AA)和乙酸(HAc)是氧化深度大、反应过程复杂、包含氧化脱氢和选择性氧种进入分子等多重步骤的多相催化过程. 从催化剂设计的角度看,适用于该反应的催化剂必须在较温和的条件下对烷烃具有氧化脱氢的能力. 钒磷混合氧化物(VPO)是目前少有的这类催化剂. 在影响其催化性能的众多因素中,n(P)/n(V)比是个关键参数;丙烷-氧共进料连续流动氧化反应的适宜n(P)/n(V)比为1.05～1.15[1～4]. 丙烷在VPO催化剂上的选择氧化按晶格氧氧化机制进行,适合于循环流化床提升管(CFBR)反应工艺[5]. CFBR工艺在大幅度提高原料中烃的浓度、抑制深度氧化、降低未反应原料的循环费用等诸多方面具有明显的优势[6],特别适用于丙烷等小分子烷烃的选择氧化. 在CFBR工艺中,与烷烃起反应的氧全部来自催化剂. 因此,为了提高经济效益,要求催化剂有尽可能大的可逆储氧量. 本文用脉冲反应器考察了催化剂P/V比对丙烷氧化反应性能的影响.     

Glycolysis of poly(ethylene terephthalate) (PET) using basic ionic liquids as catalysts

The glycolysis of poly(ethylene terephthalate) (PET) was studied using several ionic liquids and basic ionic liquids as catalysts. The basic ionic liquid, 1-butyl-3-methylimidazolium hydroxyl ([Bmim]OH), exhibits higher catalytic activity for the glycolysis of PET, compared with 1-butyl-3-methylimidazolium bicarbonate ([Bmim]HCO₃), 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and 1-butyl-3-methylimidazolium bromide ([Bmim]Br). FT-IR, ¹H NMR and DSC were used to confirm the main product of glycolysis was bis(2-hydroxyethyl) terephthalate (BHET) monomer. The influences of experimental parameters, such as the amount of catalyst, glycolysis time, reaction temperature, and dosages of ethylene glycol on the conversion of PET, yield of BHET were investigated. The results showed a strong influence of the mixture evolution of temperature and reaction time on depolymerization of PET. Under the optimum conditions of m(PET):m(EG): 1:10, dosage of [Bmim]OH at 0.1 g (5 wt%), reaction temperature 190 °C and time 2 h, the conversion of PET and the yield of BHET were 100% and 71.2% respectively. Balance between the polymerization of BHET and depolymerization of PET could be changed when the reaction time was more than 2 h and contents of catalyst and EG were changed.     

A visual test method for determining selenium(IV) with indigocarmine immobilized on silica

A solid reagent based on silica successively modified by quaternary ammonium salt and indigocarmine is proposed for the test determination of selenium(IV). The detection limit for selenium is found to be 10 μg/L using catalytic reaction of the reduction of immobilized indigocarmine by sulfide as an indicator reaction. The calibration graph is linear in the range of selenium concentrations from 50 to 400 μg/L. Alkali and alkaline-earth metals, NH ₄ ⁺ , Cl^?, NO ₃ ^? , and SO ₄ ^2? do not interfere with the determination of selenium. The interference from heavy metals is eliminated by introducing EDTA. The procedure was tested in determining selenium in preparations of vitamins and biologically active supplement.     

(BeDABCO)2Pd2Cl6 (1‐benzyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride) as a highly active catalytic system for the Stille cross‐coupling reaction under microwave irradiation

An efficient catalytic system using (BeDABCO)₂Pd₂Cl₆ was developed for the Stille cross‐coupling reaction. The substituted biaryls were produced in excellent yields in short reaction times using a catalytic amount of this catalyst in DMF at 120 °C. The ionic character of homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields and shorter reaction times than conventional heating. Benzyl DABCO as an efficient ligand and also a quaternary ammonium salt had an efficient stabilizing effect on the Pd(0) species. Copyright © 2013 John Wiley & Sons, Ltd.     

2,2-二(4-羟基-3-氨基)苯基丙烷的合成

在乙醇介质中,以Fe(OH)3／C为催化剂,用80％水合肼将2,2-二(4-羟基-3-硝基)苯基丙烷还原为2,2-二(4-羟基-3-氨基)苯基丙烷。产率99．0％,纯度98．5％。考察了10种金属离子对催化剂活性的影响,结果发现Pb^2 会引起催化剂中毒;Mg^2 ,Cu^2 和Zn^2 钝化了催化剂的催化活性;Ba^2 和Cr^3 不影响催化剂的活性;Al^3 ,Ni^2 ,Ti^3 和Ti^4 能活化催化剂,使反应速度加快,但它们单独使用时无催化活性。     

Heterogeneous Suzuki and Stille coupling reactions using highly efficient palladium(0) immobilized MCM-41 catalyst

An efficient palladium(0) immobilized MCM-41 catalytic system for C-C cross-coupling reaction has been developed. Ligand-free Pd(0)-MCM-41 catalyst can be successfully used in coupling reaction between various aryl halides including deactivated chlorobenzene with aryl borane and organotin to give biaryls in excellent yields with high turnover frequency (TOF) (the maximal TOFs are up to 6990 for the reaction of bromobenzene with phenylboronic acid). The catalyst can be recycled and reused without any loss of catalytic activity.