Unraveling the condensation reactions of heterometallic {BiNb_(4)} moieties into hybrid Bi_(x)Nb_(y)-oxo clusters with mass spectrometry

The most effective methodologies for the construction of polynuclear complexes usually take advantage of preorganized building blocks.Herein,we successfully developed a new versatile heterometallic{BiNb_(4)}moiety,which can be applied for the assembly of less explored organic-inorganic hybrid polyoxoniobates.Through controlled condensation reactions,three{BiNb_(4)}moieties can be assembled into a pair of isomeric Bi_(3)Nb_(18)clusters at different temperatures;whilst four{BiNb_(4)}moieties can be combined into two unique Bi_(4)Nb_(16)and Bi_(4)Nb_(18)tetramers in different solvents.Interestingly,we have used mass spectrometry to probe the above condensation reactions,which clearly confirmed a stepwise bottom-up assembly process by capturing the presence of bismuth subsalicylate precursors,salicylate coordinated intermediates,Nb incorporated{BiNb_(4)}moieties and the final Bi_(x)Nb_(y)-oxo clusters,respectively.Moreover,the packing modes of the{BiNb_(4)}units induce different solution behaviors,and the{BiNb_(4)}units in Bi4Nb16can be recombined by post-synthetic recrystallization in acetonitrile to produce a new tetramer Bi_(4)Nb_(18)-R.Therefore,this work provides not only a useful{BiNb_(4)}building unit but also the mechanism for their condensation,both of which will promote the future development of metal-oxo clusters.

Highly efficient Knoevenagel condensation reactions catalyzed by a proline-functionalized polyacrylonitrile fiber

A new proline-functionalized fiber catalyst was employed for the first time to catalyze the Knoevenagel condensation reactions between aromatic aldehydes and ethyl cyanoacetate or malononitrile. This fiber catalyst exhibits a high efficiency （0.5-2 tool% of catalyst with yields of 90%-99%） and excellent reusability （up to 20 times） without the need for additional treatments.

Novel and Efficient One Pot Condensation Reactions between Ketones and Aromatic Alcohols in the Presence of CrO3 Producing α,β-Unsaturated Carbonyl Compounds

We report a new, effective and simple method for preparing a,fl-unsaturated carbonyl compounds by reacting ketones and aromatic alcohols at 56 ℃ in the presence of CrO3 （CrO3 acts as an oxidant and also a catalyst） for around 10 h. The condensation reactions occurred effectively among a wide combination of ketones and alcohols. The procedure is simple and the yields can be high up to 98%. And a probable mechanism is proposed.

Amine-grafted on lanthanide metal-organic frameworks:Three solid base catalysts for Knoevenagel condensation reaction

A post-synthetic modification strategy has been used to prepare three solid base catalysts, including Er（btc）（ED）075（H2O）0.25 （2, btc = 1,3,5-benzenetricarboxylates, ED = 1,2-ethanediamine）, Er（btc）（PP）0.55（H20）0.45 （3, PP = piperazine）, and Er（btc）（DABCO）0.15（H2O）0.85 （4, DABCO = 1,4- diazabicyclo[2.2.2]octane）, by grafting three different diamines onto the coordinatively unsaturated Er（III） ions into the channels of the desolvated lanthanide metal-organic framework （Er（otc））. The resulting metal-organic frameworks were characterized by elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and N2 adsorption. Based on its higher loading ratio of the diamine, as well as its greater stability and porosity, catalyst 2 exhibited higher catalytic activity and reusability than catalysts 3 and 4- for the Knoevenagel condensation reaction. The catalytic mechanism of 2 has also been investigated using size-selective catalysis tests.

Syntheses,crystal structures,and catalytic properties of three zinc(Ⅱ),cobalt(Ⅱ)and nickel(Ⅱ)coordination polymers constructed from 5⁃(4⁃carboxyphenoxy)nicotinic acid

Three zinc(Ⅱ),cobalt(Ⅱ),and nickel(Ⅱ)coordination polymers,namely[Zn(μ^(3-)cpna)(μ-dpea)_(0.5)]_(n)(1),[Co(μ^(3-)cpna)(μ-dpey)_(0.5)]_(n)(2),and[Ni(μ^(3-)cpna)(μ-dpey)_(0.5)(H_(2)O)]_(n)(3),have been constructed hydrothermally using H_(2)cpna(5-(4-carboxyphenoxy)nicotinic acid),dpea(1,2-di(4-pyridyl)ethane),dpey(1,2-di(4-pyridyl)ethylene),and zinc,cobalt,and nickel chlorides at 160℃.The products were isolated as stable crystalline solids and were characterized by IR spectra,elemental analyses,thermogravimetric analyses,and single-crystal X-ray diffraction analyses.Single-crystal X-ray diffraction analyses revealed that three compounds crystallize in the triclinic system,space group P1.Compounds 1-3 show 2D layer structures.The catalytic activities in the Knoevenagel condensation reaction of these compounds were investigated.Compounds 1 and 2 exhibit effective catalytic activities in the Knoevenagel condensa-tion reaction at room temperature.For this reaction,various parameters were optimized,followed by the investiga-tion of the substrate scope.CCDC:2335676,1;2335677,2;2335678,3.

Fabrication and characterization of multi-scale coated boron powders with improved combustion performance:A brief review

Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion efficiency.This literature review summarizes the strategies that are used to solve the above-mentioned problems,which include coatings of boron by using fluoride compounds,energetic composites,metal fuels,and metal oxides.Coating techniques include recrystallization,dual-solvent,phase transfer,electrospinning,etc.As one of the effective coating agents,the fluorine compounds can react with the oxide shell of boron powder.In comparison,the energetic composites can effectively improve the flame temperature of boron powder and enhance the evaporation efficiency of oxide film as a condensed product.Metals and metal oxides would react with boron powder to form metal borides with a lower ignition point,which could reduce its ignition temperature.

Solid-phase Synthesis of PNA Monomer by Ugi Four-component Condensation Reaction

Peptide nucleic acids (PNA) oligomers were synthesized in most cases by peptide synthesis from N-protected monomers. In this work a new method of obtaining PNA monomer by Ugi four-component condensation reaction was tested by solid-phase synthesis. The Fmoc protected PNA monomer was build up with thymin-1-yl acetic acid, 3-methylbutyl aldehyde, Fmoc protected aminoethyl isocyanide and Gly-Wang resin.

A New Condensation Reaction of β-Keto-δ-valerolactone with Substituted Aniline

A new condensation reaction of β-keto-δ-valerolactones was developed. The condensation products are composed of a pair of isomers because of the formation ofintramolecular hydrogen bond. Their structures were confirmed by 1HNMR and elemental analysis.

Ultrasonic-assisted condensation of chitosan with salicylaldehyde

In order to synthesize an improved adsorbent for heavy metal ions,we studied the condensation reaction of chitosan with salicylaldehyde in ethanol to form a Schiff base.The effect irradiating the reaction using an ultrasonic liquid processor was contrasted with conventional methods.The IR spectra of condensed chitosan prepared by the two methods showed that their molecular structures were identical.The reaction conditions,including solvents,ultrasonic power density and irradiation time,pH,and reactant ratio,were optimized by orthogonal design.A shorter reaction time and a higher product yield were obtained using ultrasonic-assisted synthesis compared with the traditional method.A condensation degree of 89.63% was achieved using the optimized conditions:i.e.ultrasonic irradiation at 180 W for 60 min;95% ethanol as the solvent,pH 4.0,and salicylaldehyde:chitosan ratio of 6:1.

THE SOLID STATE ALDOL CONDENSATION REACTION OF ACETYLFERROCENE AND AROMATIC ALDEHYDES

The aldol condensation reactions of acetylferrocene with several aromatic aldehydes have been studied in the solid state.The results showed that they revealed different reactivities in the solid slate from that in solution and eight compounds have been prepared. Their structures have been characterized by UV,IR,1~HNMR,HS and elemental analysis.

Condensation Reaction of α-Aroyl-α-acetyl Ketene Cyclic Dithioacetals with Aromatic Aldehydes

The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.

Condensation Products from β-Keto-δ-valerolactones

Unexpected condensation products from β-keto-δ-valerolactones were obtained. Theirstructures were confirmed by 'HNMR spectrum and elemental analysis.

No-solvent Condensation Reaction of Amino Acids and their Derivatives with Pyrandione

Synthesis of a novel series of N-pyrandione substituted amino acids and their esters 3 via a condensation reaction between pyrandione and amino acid or their derivatives in excess ethyl orthoformate without solvent is described. The stereochemistry of 3 has been discussed.

THE CONDENSATION REACTION OF BIS(PERFLUOROALKANESULFONYL)METHANES WITH AROMATIC ALDEHYDES

The ccndensation reactions occurred when heating bis(perfluoroalkane- sulfonyl)methanes with aromatic aldehydes in acetic acid anhydride and gave high yields of 1-aryl-2,2-di(perfluoroalkanesulfonyl)ethylenes The perfluoroalkanesulfonyl groups R_FSO_2 are known as the strongest electron-attracting substituents^(1-2).This property is often used in the activation of C-C multiple and 2,2'-C-H bonds.The synthesis and reactions of perfluoroalkanesulfonyl substituted alkenes and alkynes are of great interest in synthetic organic chemistry^(3-6). Recently,Hanack^7 reported the preparation of 2-aryl-l-(perfluoroalkane- sulfonyl)acrylonitrile R_FSO_2C(CN)=CHAr.However,he failed to obtain the 1,1-di(perfluoroalkanesulfonyl)alkenes by the Knoevenagel reaction of bis(perfluoroalkanesulfonyl)methane with aldehydes.

New Condensation Reaction of β-keto-δ-valerolactones,Carbon Disulfide and Alkyl Halides

β-Keto-δ-valerolactones, which were obtained by reaction of acetoacetate with aldehydes or ketones, reacted with carbon disulfide, alkyl halides and a new condensation reaction was developed. The structures of the products 3 were confirmed by HNMR spectra and elemental 1 analysis.

CONDENSATION REACTION OF INACTIVATED BENZENE

A new dimolybdenum(V)complex[(C_6H_4Cl)_2C(Ph)]_2[Mo_2(μ-Cl)_3Cl_4O_2][Mo_2(μ- Cl)_2Cl_4O_2(μ-OCOPh)]has been obtained in the reaction of PhCl with benzoyl peroxide (PhCO_2)_2 and MoCl_5.Its crystal structure has been determined by X-ray diffraction meth- ods.Spectroscopic characterization of the compound and ASED-MO calculation of the trityl cation are reported.

Preparation of Aryl-Substituted Sulfonium by Condensation of Biphenyl Sulfoxides with Aromatic Compound

Three kind of aryl-substituted tri-benzyl sulfonium salts [ （4-phX）phSph2 ] PF6 [ X = S, O ] were prepared by the condensation of biphenyl sulfoxide with biphenyl sulfide, biphenyl ether or 1, 1＇ -biphenyl in the presence of polyphosphoric acid which can be used as dehydrate agent. The reaction condition was mild, such as reaction temperature between 40- 50 ℃ ,reactive time 2- 3 h, the yield of 4-（phenylthio）triphenylsulfonium hexafluorophosphate was 87.6%. The three kind sulfonium salts show better curing character to epoxy resin.

THE SECONDARY REACTION IN THE CONDENSATION OF 1-METHYL-2-METHYLTHIO-IMIDAZOLINE WITH ACTIVE METHYLENE COMPOUNDS

Mono-substituted heterocyclic ketene aminals are formed by the reaction of 1-methyl-2-methylthio-imidazoline with active methylene compounds containinq an acetyl or benzoyl group by the elimination of both a methylthio and an acyl group.This is resulted by the secondary reactio of the produced methanethiol to attack the more active carbonyl group.

Synthesis of N,N'-bis(2,4-dinitrobenzofuroxan)-3,5-dinitro-2,6-diaminopyridine

N,N'-bis(2,4-dinitrobenzofuroxan)-3,5-dinitro-2,6-diaminopy- ridine has been synthesized from 2,6-diaminopyridine and trinitrodich- lorobenzene.For this compound,the structure has been determined by ele- mental analysis,IR,HNMR and MS spectroscopy.

Sulfonated carbon materials with hydrophilic and lipophilic properties

Two acidic carbon materials （H-PRC and HS-C） were used as catalysts for the condensation reaction of methanol with formaldehyde to produce dimethoxymethane （DMM） in aqueous solution （hydrophilic system） and for the etherification of isopentene with methanol to produce tert amyl methyl ether （TAME） in toluene solution （lipophilic system）. Microcalorimetric adsorptions of water and benzene showed that the HS-C was highly hydrophilic without the lipophilicity, while the H-PRC exhibited both the hydrophilicity and lipophilicity. Thus, the HS-C was well dispersed in aqueous solution and difficult to separate from it. On the other hand, the H-PRC was highly active, more active than the acidic resin （D008） and sulfuric acid, for the synthesis of DMM in aqueous solution. The H-PRC was also highly active, more active than the HS-C, for the etherification of isopentene with methanol to produce TAME in toluene solution, probably owing to its amphiphilic surface property as well as its strong surface acidity as measured by the microcalorirnetric adsorption of NH3.