Aqueous media carboxylative cyclization of propargylic amines with CO2 catalyzed by amphiphilic dendritic N-heterocyclic carbene–gold(I) complexes

We prepared amphiphilic dendritic N-heterocyclic carbene (NHC)–gold(I) complexes having poly(ethylene glycol) units at the peripheral layer. By employing 1 mol % of the dendritic NHC–gold(I) catalyst, the aqueous media carboxylative cyclization of propargylic amines proceeded smoothly to provide the corresponding 2-oxazolidinone under atmospheric pressure of CO₂ at room temperature.     

Synthesis,characterization and the rapid response property of the temperature responsive PVP-g-PNIPAM hydrogel

In this study, a poly(N-vinylpyrrolidone)-graft-poly(N-isopropylacrylamide) hydrogel (PVP-g-PNIPAM) was synthesized through the “grafting from” process. Grafting of temperature responsive poly(N-isopropylacrylamide) (PNIPAM) brushes was carried out from the poly(N-vinylpyrrolidone) (PVP) synthesized with free radical polymerization and functionalized with ATRP initiator, PVP–Br, which was performed through a bromination reaction between pendant allylic groups of the PVP and N-bromosuccinimide (NBS). The structure of the initiator and PVP-g-PNIPAM was characterized by ultraviolet and visible (UV/Vis) absorption, nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) measurements. Scanning electron microscope (SEM) morphology measurement displayed some dendritic grafted chains dangling onto the pore wall of the hydrogel.The characteristic in response to the change in environmental temperature was investigated by the fluorescence anisotropy and UV/Vis transmittance measurements. The results showed that the PVP-g-PNIPAM hydrogel exhibited rapid response to the change in environmental temperature due to free and mobile graft chains compared with the P(VP-co-NIPAM) hydrogel, which was prepared by free radical copolymerization in this work.     

Efficient deprotection of N-benzyloxycarbonyl group from amino acids by hydroxyapatite-bound Pd catalyst in the presence of molecular hydrogen

Hydroxyapatite-bound Pd catalyst was found to be highly effective for the deprotection of N-benzyloxycarbonyl group from amino acids in the presence of molecular hydrogen. The catalyst was also applicable to the hydrogenolysis of a sterically encumbered core-Z-protected poly(amido amine) dendrimer, affording the dendritic amino compound in 99% yield.     

Synthesis of novel well-defined chain-end-functionalized polystyrenes with dendritic chiral ephedrine moieties and their applications as highly enantioselective diethylzinc addition to N-diphenylphosphinoyl arylimines

A series of novel well-defined chain-end-functionalized polystyrenes having 2, 4, 8, and 16 chiral ephedrine moieties dendritically distributed at their hyperbranched chain-ends were quantitatively synthesized. Their well-defined architectures were fully confirmed by elemental analysis, FTIR, SEC as well as by ¹H and ¹³C NMR spectroscopies. These polymers were precisely controlled in the molecular weight and molecular weight distribution as well as well-defined in chain-end-functionalities. These dendritic chiral polymers serve as highly enantioselective chiral ligands in the enantioselective addition of diethylzinc to a series of N-diphenylphosphinoyl arylimines. Among them, chiral dendrimer having eight ephedrine moieties at the chain-ends afforded the corresponding enantiomerically enriched phosphinoylamides in good to high yields with enantioselectivities up to 93% ee. The obtained enantioselectivities are comparable with those obtained by using N-benzylephedrine and its corresponding copolymer as chiral ligands.     

Design,synthesis and structure of new dendritic melamines. First use of a tandem C-2-substituted serinol—O,O-masked 4-piperidone as a peripheral unit in iterative synthesis

The iterative chemoselective amination of cyanuric chloride to dimers of new G-2 dendritic N-substituted-2,4,6-triamino-s-triazines (melamines) having C-2-substituted 2-aminopropane-1,3-diols (‘serinols’) in tandem with the ethylene ketal of 4-piperidone as peripheral units is reported. The structure as a function of increasing molecular size was studied by NMR spectroscopy, DFT calculation and AFM imaging. A concise nomenclature defining the restricted rotational phenomena about the newly created C(s-triazine)–N(exocyclic) partial double bonds, seen as axes of (pro)diastereomerism, is used. We propose a new form of frontier rotamerism for the dendrimer surface, which operates over a long range.     

The synthesis and immune stimulating action of mannose-capped lysine-based dendrimers

The syntheses of monodisperse lysine dendrimers, capped with two to sixty-four mono-, di- and tri-α-d-mannopyranosyl residues are described. These syntheses used reactive N-hydroxysuccinimide esters to ensure complete reaction of dendrimer amines with the mannosylating reagents. The purities of the dendrimers were established by RP-HPLC and MALDI-TOF mass spectrometry and were found to be excellent. The relative ability of these glycodendrimers to induce dendritic cell maturation was measured, however, no significant trends were observed.     

Preparation and characterization of dendrimer-star PNIPAAM using dithiobenzoate-terminated PPI dendrimer via RAFT polymerization

Two dendritic reversible addition-fragmentation transfer (RAFT) agents with 8 and 16 terminal dithiobenzoate (DTB) groups on the surface of poly(propylene imine) (PPI) dendrimers (generation 2.0 and 3.0, respectively) were successively prepared, and they were used in the RAFT polymerization of N-isopropylacrylamide (NIPAAM). The polymerization kinetics was confirmed to pseudo-first-order behavior. The ¹H NMR and GPC analyses show that the dendrimer-star den (NIPAAM)_x (x = 8 or 16) prepared by RAFT method has well-defined structure, controlled molecular weight and low polydispersities (PDI < 1.3). The aqueous solution prepared from dendrimer-star PNIPAAM showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST.     

钯纳米粒子的形貌可控合成与催化性能

借助于一种全新的表面活性剂N,N-dimethyloctadecylammonium bromide acetate sodium（OTAB-Na）,成功实现了对小尺寸钯纳米粒子微结构的控制。通过对合成条件的微扰,高度均匀且分散性良好的枝化结构和凹面体结构的钯纳米粒子被成功地制备。催化测试（利用氨硼烷作为氢化试剂来还原4-硝基苯酚为4-胺基苯酚）发现,钯纳米粒子的催化活性与其微观纳米结构相关,其中枝化结构的钯纳米粒子表现出了更为突出的催化性能。     

Use of Stille-type cross-coupling as a route to oligopyridylimines

The new tin reagents, 2-(n-Bu₃Sn)-6-{C(R)OCH₂CH₂O}-C₅H₃N, (R=H a, Me b), have been employed in Stille-type cross-coupling reactions with a range of oligopyridylbromides generating, following a facile deprotection step, a series of formyl- and acetyl-functionalised oligopyridines. Condensation reactions with 2,6-diisopropylaniline has allowed access to families of novel sterically bulky multidentate N,N,N,N (tetradentate), N,N,N,N,N (pentadentate), N,N,N,N,N,N (sexidentate) and N,N,N,N,N,N,N (heptadentate) nitrogen donor ligands. This work represents a straightforward and rapid synthetic route for the preparation of oligopyridylimines, which are expected to act as useful components for the self-assembly of polymetallic complexes.     

Ultrasound induced formation of organogel from a glutamic dendron

New l-glutamic acid based dendritic compounds: N-(2-naphthacarbonyl)-l-glutamic acid diethyl ester (NGE) and N-(2-naphthacarbonyl)-1,5-bis(l-glutamic acid diethyl ester)-l-glutamic diamide (NBGE) were designed. Although NGE could not form any gels in common solvents, NBGE could form stable gels in hexane, toluene, and water under ultrasound. Three dimensional network structures composed of fibers with various diameters were observed in the gel by SEM and TEM. FTIR spectral measurement revealed that ultrasound during cooling of the solution could destroy some of the hydrogen bond interactions and caused the gel formation. In solution, no CD signal was detected because the naphthyl chromophore is far from the chiral center. In the gel, however, CD signals assigned to the naphthyl group were observed, which indicated that the chirality of the chiral center could be transferred to the chromophore in the supramolecular organogel system.     

Antibacterial activity of N-quaternary chitosan derivatives: Synthesis, characterization and structure activity relationship (SAR) investigations

Quaternary N-(2-(N,N,N-tri-alkyl ammoniumyl and 2-pyridiniumyl) acetyl) derivatives of chitosan polymer, chitooligomer, and glucosamine (monomer) were synthesized for the purpose of investigating the structure activity relationship (SAR) for the antibacterial effect. Novel methods were used in the synthesis. The final chitosan and chitooligomer derivatives could thus be obtained in two steps without prior protection of the hydroxyl groups. However, in order to obtain chitosan derivatives with the bulky N,N-dimethyl-N-dodecyl- and N,N-dimethyl-N-butyl side chains three steps were needed, starting from 3,6-O-di-tert-butyldimethylsilyl chitosan (3,6-O-di-TBDMS chitosan) as the key intermediate. The quaternary ammoniumyl acetyl derivatives of glucosamine were synthesized from glucosamine or tetra-O-acetylglucosamine. N,N,N-trimethyl chitosan (TMC) was used as reference compound for investigation of antibacterial activity. Clinical Laboratory Standard Institute (CLSI) protocols were used to determine MIC and MLC for activity against clinically important Gram-positive strains Staphylococcus aureus (ATCC 25923), and S. aureus (MRSA) (ATCC 43300), and Gram-negative strains of Escherichia coli (ATCC 25922), P. aeriginosa (ATCC 27853) and Enterococcus facialis (ATCC 29212). The MIC values for the compounds ranged from 8 to ?8192 mg/L. In general the N-(2-(N,N-dimethyl-N-dodecyl ammoniumyl) acetyl) derivatives of chitooligomer and glucosamine monomer were more active against bacteria than derivatives with shorter alkyl chains. In contrast the N-(2-(N,N-dimethyl-N-dodecyl ammoniumyl) acetyl) derivatives of chitosan were less active than derivatives with N-(2-N,N,N-trimetylammoniumyl) acetyl or N-(2-(N-pyridiniumyl) acetyl) quaternary moiety. N,N,N-trimethyl chitosan (TMC) was the most active compound in this study.     

Synthesis of 2-methyl-N-(2,2,2-trichloroethylidene)- and 2-methyl-N-(2,2,2-trichloroethyl)benzenesulfonamides from N,N-dichloro-2-methylbenzenesulfonamide and trichloroethylene

The reaction of N,N-dichloro-2-methylbenzenesulfonamide with trichloroethylene gave a new representative of highly electrophilic N-sulfonyl polyhaloaldehyde imines, 2-methyl-N-(2,2,2-trichloroethylidene) benzenesulfonamide. High reactivity of the product was demonstrated in the addition of water and 2-methylbenzenesulfonamide and reactions with benzene, toluene, anisole, thiophene, and 2-chlorothiophene. N,N-Dichlorobenzenesulfonamides and N,N-dichlorotrifluoromethanesulfonamide failed to react with 1,1,3,3,4,4-hexachlorobut-1-ene and 1,1,2,3,4-pentachlorobuta-1,3-diene under the conditions ensuring formation of N-(2,2,2-trichloroethylidene)arenesulfonamides from N,N-dichloroarenesulfonamides and trichloroethylene.     

New investigation of Vilsmeier-type reaction using pyrazolones with various amides

New investigation of Vilsmeier-type reaction was evaluated to realize the solvent effect by using pyrazolones to react with various of amides, including formamide, N-methylformamide, N-propylformamide, N-tert-butylformamide, N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), N,N-dipropylformamide (DPF), N,N-diisopropylformamide, N,N-dibutylformamide, piperidine-1-carbaldehyde, and pyrrolidine-1-carbaldehyde, in the presence of phosphorous oxychloride POCl₃. The unexpected resulting products were observed in this work according to the difference chemoseletivities of substituted amides. The plausible reactive pathways were proposed to explain the experimental result.     

Étude de la complexation des lanthanides trivalents par les six isomères de l'acide diaminocyclohexane-tétraacétique : Partie 3. Relation entre les Constantes d'Acidité et la Structure Moleculaire des Chélatants

(Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 3. Relationship between the acidity constants and the molecular structure of the ligands.)Potentiometric measurements of the acidity constants of the six isomers of diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA) are reported for an ionic strength of 1 mol l^?1 (KCl) at 25°C. The values of the two constants K_a3 and K_a4 are correlated with the maximum N—N distance for each ligand. Ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) and some homologous ligands, including specially synthesized, 1,8-diaminooctane-N,N,N′,N′-tetraacetic acid and 1,10-diaminodecane-N,N,N′,N′-tetraacetic acid, are studied under the same conditions. It is proved that there is a relationship between the molecular structure and the affinity for protons.     

Dissociation energy of N-H bonds in diatomic aromatic amines

The dissociation energies of N-H bonds (D, kJ/mol) were calculated by the intersecting parabolas method using the kinetic data for the following aromatic diamines: para-phenylenediamine (359.8), N,N′-dimethyl-para-phenylenediamine (348.9), N-dimethyl-N′-methyl-para-phenylenediamine (342.4), N,N′-diphenyl-para-phenylenediamine (352.8), N,N′-diphenylethylenediamine (372.7), N,N′-diheptylethylenediamine (373.3), N,N′-di-(4,4′-ethoxyphenyl)ethylenediamine (363.3), N,N′-di-(4,4′-diisopropylphenyl)-para-phenylenediamine (344.6), 4-{[dimethyl(4-phenylamino)phenoxy)silyl]oxy}-N-phenylaniline (353.4), N,N′-di-β-naphthyl-para-phenylenediamine (354.6), N,N′-di-β-naphthoxy-para-phenylenediamine (353.7), 1,1′-dinaphthyl-2,2′-bis-N,N′-phenyldiamine (372.9), 1,1′-dinaphthyl-2,2′-bis-N,N′-β-naphthyldiamine (384.2), and 2,6-bis[(1E)-1-(2-phenylhydrazin-1-ylidene)ethyl]pyridine (367.9). Individual dissociation energies for the two N-H bonds were determined in N-phenyl-N′-isopropyl-para-phenylenediamine: D(PhN-H) = 352.5 and D(Me₂CHN-H) = 348.7 kJ/mol.     

[4+1] Cycloaddition of N-acylimine derivatives with isocyanides: efficient synthesis of 5-aminooxazoles and 5-aminothiazoles

[4+1] Cycloaddition reaction between isocyanides and N-acylimine derivatives generated from N-acyl N,O-acetals acting as isocyanophiles has been developed. These reactions proceeded smoothly and cleanly to afford the corresponding 5-aminooxazoles in high yields. This reaction was extended to the syntheses of 5-aminothiazoles by using N-thioacyl N,O-acetals. A wide range of N-acyl N,O-acetals, N-thioacyl N,O-acetals, and isocyanides were found to be applicable to this reaction.     

Fluorsilylsubstituierte N,N- und N,O-bis(trimethylsilyl)-hydroxylamine

Fluoro- und aminofluoro-silanes react with the lithium salt of N,O-bis(trimethylsilyl)hydroxylamine under LiF elimination and substitution. Alkyl- and amino-fluorosilanes give O-fluorosilyl-N,N-bis(trimethylsilyl)hydroxylamines, arylfluorosilanes give N-fluorosilyl-N,O-bis(trimethylsilyl)hydroxylamines. By the further reaction of O-difluorosilyl-N,N-bis(trimethylsilyl)hydroxylamine with the lithiated hydroxylamine, O,O′-fluoromethylsilyldi[N,N-bis(trimethylsilyl)hydroxylamine] is formed. On heating N-difluorophenylsilyl-N,O-bis(trimethylsilyl)hydroxylamine di[fluorophenylsilyl(methyl)amino]pentamethylsiloxane is formed by methyl group migration. The NMR and mass spectra of the compounds are reported.     

Microwave-assisted synthesis of N,N-bis-(2-pyridylmethyl)amine derivatives. Useful ligands in coordination chemistry

Microwave-assisted synthesis of the ligands N,N-bis-(2-pyridylmethyl)amine (BMPA), N-(methylpropanoate)-N,N-bis-(2-pyridylmethyl)amine (MPBMPA), N-(propanamide)-N,N-bis-(2-pyridylmethyl)amine (PABMPA), PNBMPA (N-(3-propionitrile)-N,N-bis-(2-pyridylmethyl)amine), N-(3-aminopropyl)-N,N-bis-(2-pyridylmethyl)amine (APBMPA), and lithium N-(proponoate)-N,N-bis-(2-pyridylmethyl)amine (LiPBMPA) are reported. High yields and short reaction time were obtained for condensation and Michael addition.     

Copper(I) catalysis: Synthesis of N,N′-diarylated and N-aryl,N′-formylated chiral C2-symmetric diamines

Chiral N,N′-diaryl C₂-symmetric diamines and N-aryl,N′-formyl-trans-(1R,2R)-diaminocyclohexane are readily accessed by copper catalyzed N,N′-diarylation and N-aryl,N′-formylation of trans-(1R,2R)-diaminocyclohexane with aryl bromides. N,N′-diarylation using (R)-1,1′-binaphthyl-2,2′-diamine and iodobenzene gave the corresponding (R)-N,N′-diphenyl-1,1′-binaphthyl-2,2′-diamine derivative in 83% yield.     

Recent progress in controlled radical polymerization of N-vinyl monomers

This review summarizes recent advances in the controlled radical polymerization of N-vinyl monomers, such as N-vinylcarbazole, N-vinylindole derivatives, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinylacetoamide derivatives, N-vinyl(na)phthalimides, N-vinylimidazolium salts, and N-vinyltriazoles. Recent significant progress of controlled radical polymerization of these N-vinyl monomers has allowed for the synthesis of well-defined functional polymers having various architectures, including block copolymers, branched polymers (stars, star block copolymers, miktoarm star copolymers, and graft copolymers), and hybrids. Characteristic properties, assembled structures, and three-dimensional architectures of these functional polymers derived from N-vinyl monomers are briefly introduced.