Palladium-catalyzed Suzuki couplings using a novel diaminophosphine oxide as ligand

A novel diaminophosphine oxide was synthesized and applied as ligand in palladium-catalyzed Suzuki couplings reaction of aryl bromides and chlorides.The coupling reaction proceeded smoothly at mild conditions using 2 mol%Pd₂（dba）₃ in the presence of BuOK.     

Microwave assisted,ligand free,copper catalyzed reaction of aryl halides with phenyl urea

The ligand free coupling reaction of phenyl urea with different functionalized aryl halides in the presence of air stable Cu₂O and t-BuOK as a base gives symmetrical and unsymmetrical diarylureas in relatively high yields.This method is milder than the palladium catalyzed arylation and avoids the use of toxic phosphine ligand.     

A copper- and amine-free Sonogashira reaction employing chlorophosphine as new and efficient ligand

An efficient palladium-catalyzed copper- and amine-free Sonogashira coupling reaction of aryl bromides and chlorides was studied using a sterically hindered monooxychlorophosphine as new ligand.The use of 2 mol%Pd（OAc）₂ in the presence of K₂CO₃ allows the coupling reaction to proceed at mild condition with good to excellent yields.     

Thiamine hydrochloride(VB1):An efficient catalyst for one-pot synthesis of α-aminophosphonates under ultrasonic irradiation

An efficient synthesis of novelα-aminophosphonates by the reaction of aldehydes and amines with triethyl phosphite in the presence of the easily available,inexpensive,and nontoxic catalyst thiamine hydrochloride(VB1).This method affords theα-aminopho-sphonates under the influence of ultrasound irradiation in aqueous medium,in short reaction times(4-6 min),high yields(85-95%), with improved purity.The process is green,mild,inexpensive and excellent yields are the main compensation of this procedure.     

An efficient method for the N-arylation of phenylurea via copper catalyzed amidation

The coupling reaction of phenylurea with different functionalized aryl halides in the presence of air stable CuI,N,N-dimethylethylenediamine as a ligand,and K₃PO₄ as a base gives symmetrical and unsymmetrical diarylureas in relatively high yields.This method is milder than the palladium catalyzed arylation and avoids the use of toxic phosphine ligands.     

Sulfamic acid as a reusable and green catalyst for efficient and simple synthesis of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in water or methanol

A series of 2,3-dihydroquinazolin-4（1H）-ones have been synthesized in good to excellent yields through direct cyclocondensation of anthranilamide and aryl aldehydes or ketones in water or methanol under mild conditions.The reaction was efficiently promoted by 10 mol%sulfamic acid（SA,H₂NSO₃H） and the catalyst could be recovered easily after the reactions and reused without evident loss of reactivity.     

Amide as an efficient ligand in the palladium-catalyzed Suzuki coupling reaction in water/ethanol under aerobic conditions

Amide,which is derived from proline and is inexpensive and air-stable,has been synthesized and characterized by ¹H NMR,¹³C NMR,and MS.It was found to be an efficient ligand in the palladium-catalyzed Suzuki cross-coupling reaction.In the Pd/amide catalytic system,aryl bromides can be coupled with phenylboronic acid in ethanol/water（1:2;v/v） in excellent yields even with a low Pd loading of 0.01 mol%.Moreover,the scope of the reaction is broad,and a wide variety of functional groups are tolerant.     

CO2 as Both a Selective Agent and Reaction Media in Palla-dium-Catalyzed Reductive Ullmann-Type Coupling Reaction

Carbon dioxide as both a selective agent and reaction media in the palladium-catalyzed Ullmann-type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carbon dioxide and the chemoselectivity shifted toward the palladium-catalyzed Ullmann-type coupling reaction. In liquid carbon dioxide, homocoupling reactions of aryl halides, including less reactive aryl chlorides, were carried out smoothly in moderate to good yields using Pd/C, zinc, and H2O as the catalytic system at room temperature.     

Synthesis and Antifungal Activity of Novel Chiral α-Aminophosphonates Containing Fluorine Moiety

Chiral α-aminophosphonates were synthesized using （R） or （S）-1-phenylethylamine in the presence of BF3·Et2O under microwave irradiation in moderate to good yields. The new compounds were identified by ^1H NMR, ^19F NMR, IR and elemental analysis. Their antifungal activities were evaluated and some compounds were found to exhibit excellent antifungal activities. To the best of our knowledge, this is the first report on antifungal activity of chiral α-aminophosphonates containing fluorine moiety.     

Helical secondary structures and supramolecular tilted chirality in N-terminal aryl amino acids with diversified optical activities

Helix structures at atomic/molecular level have not been found in self-assembled peptide seque nce with less than three residues.As β-sheet supramolecular secondary structures have been discovered in solidstate amino acids,we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state,which determines the optical activities of the adjacent aryl groups.The carboxylic acid-involved asymmetric H-bonds in N-te rminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups.In most cases,supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences,of which handedness and helical pitch are determined by the H-bond modalities.Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled,which was verified by the computational results based on density functional theory.Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus.This study reveals the generic existence of chiral supramolecular structure s in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships,which could guide the rational design and screening of chiroptical supramolecular materials.     

Synthesis of O-glycosylα-aryl nitrones

<正>α-Aryl nitrone are one of the most useful kinds of nitrones and have been extensively explored in recent years.However,the sugar moieties have not been introduced into these molecules before.We presented here an efficient synthesis ofα-aryl nitrone Oglycosides via condensation of N-substituted hydroxylamine and aryl aldehydes glycosides in benzene.     

The α and β domains of human metallothionein-3 co-operatively protect against Aβ1-42-Cu2+ cytotoxicity

Cytotoxicity of A β with redox active metals in neuronal cells has been implicated in the progression of Alzheimer’s disease （AD）.Zn₇MT-3 protects cell against Aβ-Cu²⁺ toxicity.The roles of single domain proteins（α/β） andα-βdomain-domain interaction of Zn₇MT-3 in its anti-Aβ_1-42-Cu²⁺ toxicity activity were investigated herein.Aβ_1-42 and four mutants of human MT3 （α/βdomain,β（MT3）-α（MTl） and A31-34） were prepared and characterized.Aβ_1-42-Cu²⁺ induced hydroxyl radical and ROS production with/without Zn-MTs were measured by fluorescence spectroscopy and DCFH-DA in living cells,respectively.These results indicate that the two domains form a co-operative unit and each of them is indispensable in conducting its bioactivity.     

Investigating the Absorption and Desorption Behavior of Methylene Chloride in the Poly(aryl ether ketone) Film with Different Crystallinities

Poly(aryl ether keton e)(PAEK) films with different crystallinities were obtained by controlling the cooling rate,which were subjected to the absorption and desorption of methylene chloride(CH₂Cl₂).We employed attenuated total reflection Fourier transform infrared(ATR-FTIR)spectroscopy analyses to investigate the diffusion behavior of CH₂Cl₂ in PAEK films with different crystallinities.According to the Fickian diffusion model,the calculated diffu sion ...     

PPA-SiO_2 catalyzed efficient synthesis of polyhydroquinoline derivatives through Hantzsch multicomponent condensation under solvent-free conditions

Silica gel-supported polyphosphoric acid（PPA-SiO₂） was found to be an efficient catalyst for the one-pot four-component Hantzsch condensation reaction of aryl aldehydes,dimedone,ethyl acetoacetate and ammonium acetate to afford the corresponding polyhydroquinoline derivatives in high yields.The main advantages of the present approach are short reaction times,clean reaction profiles,simple experimental and workup procedures.     

Synthesis of 3-(aryl)-2-thioxo-2,3-dihydroquinazolin-4(1H)-one derivatives using heteropolyacids as green,heterogeneous and recyclable catalysts

Reaction of isatoic anhydride with aniline derivatives gave 2-amino-N-(aryl)benzamides.The latters reacted with phenyli-sothiocyanate in the presence of heteropolyacids in various solvents which afforded 3-(aryl)-2-thioxo-2,3-dihydroquinazolin- 4(1H)-one derivatives.The effects of various heteropolyacids including Preyssler and Keggin on the yields and reaction times have been investigated.     

钨酸钠催化芳香腈高选择性氧化制备芳香酰胺

 The preparation of aryl amides by selective oxidation of aryl nitriles using sodium tungstate as catalyst and sodium percarbonate or sodium carbonate-hydrogen peroxide as the oxidant in a methanol and water solution was studied. Aryl nitriles were converted to aryl amides with very high selectivity of 95%～100% at room temperature. The reactivity of aryl nitriles decreased with increasing their branched chain length. In the oxidation of tolunitriles, the oxidation rate of p-tolunitrile and m-tolunitrile was very fast, but the oxidation rate of o-tolunitrile was very slow. The oxidation rate of p-haloid aryl nitriles and p-nitro aryl nitrile decreased in the order p-nitrobenzonitrile＞p-chlorobenzonitrile＞p-bromobenzonitrile, while the selectivity for aryl amides was maintained at a high level of 98%～100%. The comparison of the two oxidants showed that when sodium carbonate-hydrogen peroxide was used as oxidant, the oxidation rate and selectivity were better than that when percarbonate was used. The sodium tungstate catalyst and carbonate can be reused and the catalytic activity and selectivity did not change if a suitable amount of hydrogen peroxide was supplied. This work provides a convenient method for the preparation of aryl amides from aryl nitriles under very mild reaction conditions.     

First Synthesis of a Series of New Natural Glucosides

Alkyl glucoside 1 and aryl glycosides 2-4 were highly stereospecifically synthesized over 4-6 steps from commercially available starting materials. The coupling reaction of the acetobromo-α-D-glucose with the unprotective dihydroxy aglycon in the presence of silver oxide, or with aromatic aglycon in the presence of sodium hydroxide produced the key intermediate. Only β-configuration glycosides were formed in this procedure. The synthesis of all these glycosides was reported for the first time.     

Copper and amine free Sonogashira cross-coupling reaction catalyzed by efficient diphosphane-palladium catalyst

The commercially available diphosphane ligand MeO-BIPHEP was first investigated in the palladium-catalyzed Sonogashira reaction in the absence of copper and amine.The coupling of various aryl bromides and aryl chlorides with phenylacetylene gave moderate to excellent yields.     

Polyethylene glycol radical-initiated aerobic propargylic oxidation in dense carbon dioxide

The selective aerobic oxidation of alkynes to correspondingα,β-acetylenic ketones was achieved in polyethylene glycol/dense CO₂/O₂ biphasic system without any catalyst or additive.The effects of reaction parameters,e.g.temperature,CO₂ pressure,PEG molecular weight and loading on the reaction were carefully examined.Moreover,various substrates worked well in the presence of PEG 1000 under 5 MPa of CO₂ and 2 MPa of O₂ at 100℃for 12 to 24 h and acceptable yield and selectivity could be obtained in most cases.Preliminary mechanistic investigations were also discussed.     

The efficient synthesis of 14-alkyl or aryl 14H-dibenzo[a,j]xanthenes catalyzed by bismuth(Ⅲ)chloride under solvent-free conditions

An efficient method for the synthesis of 14-alkyl or aryl 14H-dibenzo[a,j]xanthene derivatives by the reaction of β-naphthol,and aldehydes in the presence of a catalytic amount of bismuth（Ⅲ） chloride（BiCl₃） under solvent-free conditions at 110℃is described.Aliphatic and aromatic aldehydes were used in the reaction and in all cases the desired products were synthesized successfully.This reaction was studied under different temperatures;the maximum yield was obtained in a short reaction period at 110℃.The method offers the advantages of high yields,short reaction times,simplicity and easy workup compared to the conventional method of syntheses.