A Facile and Practical One-Pot Synthesis of beta-Oxo Thioamides from beta-Oxo Amides and Isothiocyanates

A facile and practical one-pot synthesis of beta-oxo thioamides from beta-oxo amides has been developed. By treatment with isothiocyanates in ethanol in the presence of potassium carbonate, a series of beta-oxo amides was converted, under reflux, in high yields into the corresponding beta-oxo thioamides.

Synthesis and electrochemical applications of gold nanoparticles

This review covers recent advances in synthesis and electrochemical applications of gold nanoparticles (AuNPs). Described approaches include the synthesis of AuNPs via designing and choosing new protecting ligands; and applications in electrochemistry of AuNPs including AuNPs-based bioelectrochemical sensors, such as direct electrochemistry of redox-proteins, genosensors and immunosensors, and AuNPs as enhancing platform for electrocatalysis and electrochemical sensors.

Efficient one-pot synthesis of highly substituted pyridin-2(1H)-ones via the Vilsmeier-Haack reaction of 1-acetyl,1-carbamoyl cyclopropanes

A facile and efficient one-pot synthesis of highly substituted pyridin-2(1H)-ones is developed via the Vilsmeier-Haack reaction of readily available 1-acetyl,1-carbamoyl cyclopropanes, and a mechanism involving sequential ring-opening, haloformylation, and intramolecular nucleophilic cyclization reactions is proposed.

One-pot synthesis of polyimides via Ni-catalyzed coupling of bis(chlorophthalimide)s

A one-pot synthesis method for the preparation of polyimides containing biphenyl units was developed via nickel-catalyzed coupling reaction of bis(chlorophthalimide)s which were prepared from chloroplithalic anhydrides and diamines in xylene. The resulting polyimides had inherent viscosities of above 0.60dL g(-1). In the meantime, the copolymerizations from a mixture of three isomeric bis(chlorophthalimide)s gave the polymers with inherent viscosities of 0.36-0.55 gdL(-1). The solubility and film formability of the copolymers were better than those of homopolymers from bis(4-chlorophthalimide). The 10% weight loss of these polyimides was between 470 and 531 degrees C.

One-step preparation and characterization of poly(propyleneimine) dendrimer-protected silver nanoclusters

Highly stable silver nanoclusters with narrow size distribution have been prepared by heating a third-generation poly(propyleneimine) dendrimer/AgNO3 aqueous solution without the additional step of introducing other reducing agents and protect agents. UV-vis absorption, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and X-ray diffraction (XRD) have been used to characterize the resulting products. The as-obtained sample was in coexistence of Ag and Ag2O. It also suggested that increasing temperature resulted in both the decrease in number of small particles and the increase in size of large particles.

Novel acidic porous clay heterostructure with highly ordered organic-inorganic hybrid structure: one-pot synthesis of mesoporous organosilica in the galleries of clay

A new class of organic-inorganic hybrid porous clay heterostructures (HPCHs) have been prepared through the surfactant-directed assembly of organosilica in the galleries of montmorillonite. The reaction involved hydrolysis and condensation of phenyltriethoxysilane and tetraethoxysilane in the presence of intragallery surfactant templates (dodecylame and cetyltrimethylammonium ion). The surfactant templates were removed from the pores by solvent-extraction. The products were characterized by X-ray diffraction (XRD), N-2 adsorption, solid-state Si-29 and C-13 NMR, and FTIR. XRD patterns indicated a regular interstratification of the clay layers for HPCHs. Depending on loading of phenyl groups, HPCHs had BET surface areas of 390-771 m(2) g(-1), pore volumes of 0.3-0.59 cm(3) g(-1), and the framework pore sizes in the supermicropore to small mesopore range (1.2-2.6 nm). HPCHs were hydrophobic and acidic.

Synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl primary amines

A new method for syntheses of hyperbranched poly(ester-amide)s from commercially available A(2) and CBx type monomers has been developed on the basis of a series of model reactions. The aliphatic and semiaromatic hyperbranched poly(ester-amide)s with multihydroxyl end groups are prepared by in situ thermal polycondensation of intermediates obtained from dicarboxylic acids (A(2)) and multihydroxyl primary amines (CBx) in N,N-dimethylformamide. Analyses of FTIR, H-1 NMR, and C-13 NMR spectra revealed the structures of the polymers obtained. The MALDI-TOF MS of the polymers indicated that cyclization side reactions occurred during polymerization. The hyperbranched poly(ester-amide) s contain configurational isomers observed by C-13 and DEPT C-13 NMR spectroscopy. The DBs of the polymers were determined to be 0.38-0.62 by H-1 NMR or quantitive C-13 NMR and DEPT 135 spectra. These polymers exhibit moderate molecular weights, with broad distributions determined by size exclusion chromatography ( SEC), and possess excellent solubility in a variety of solvents such as N, N- dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and ethanol, and display glass-transition temperatures (T(g)s) between -2.3 and 53.2 degrees C, determined by DSC measurements.

One-step preparation and characterization of PDDA-protected gold nanoparticles

Poly(diallyl dimethylammonium) chloride (PDDA), an ordinary and watersoluble, cationic polyelectrolyte, was investigated for its ability to generate and stabilize gold colloids from a chloroauric acid precursor. In this reaction, PDDA acted as both reducing and stabilizing agents for gold nanoparticles (AuNPs). More importantly, PDDA is a quaternary ammonium polyelectrolyte, which shows that the scope of the reducing and stabilizing agents for metal nanoparticles can be extended from the amine-containing molecules to quaternary ammonium polyelectrolytes or salts. UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and Fourier transform infrared (FTIR) were used to characterize the synthetic AuNPs. The PDDA-protected AuNPs obtained are very stable and have relative narrow size distribution.

One-pot synthesis of polyetherimides from bis(chlorophthalimide) and dichlorodiphenylsulfone in diphenylsulfone

Polyetherimides and copolymers have been synthesized in one pot from bis(chlorophthalimide), dichlorodiphenylsulfone, and bisphenolate using diphenylsulfone as the solvent. The inherent viscosities of the obtained polyimides are in the range of 0.32-0.72 dL/g, and the structures of polyimides were confirmed by IR and elemental analyses. All of the polyimides have good solubility in common organic solvents. The 5% weight-loss temperatures of the polyimides were 429-507 C in air. The glass transition temperatures (T3) of 4,4'-(9-fluorenylidene) diphenol-based polyimides are in the range of 253-268 degrees C. The Tg of bisphenol A-based polyimides is in the range of 198204 degrees C, while the T-g change inconspicuously when the ratios of diphenylsulfone increase. The wide-angle X-ray diffraction showed that all polyimides prepared are amorphous.

One-pot synthesis and characterization of novel silver-gold bimetallic nanostructures with hollow interiors and bearing nanospikes

One-pot preparation of shell-type silver-gold bimetallic nanostructures with hollow interiors and bearing nanospikes, based on colloid seed-engaged replacement reaction and colloid-mediated deposition reactions, has been reported. Heating-induced evolution of Ag-Au bimetallic nanoshells can lead to spontaneous production of nanospikes on the colloid surface. The hollow interior structure and bimetallic nature of the as-prepared colloids are characterized by transmission electron microscopy (TEM), UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Diffusion-limited kinetics modeling of one-step polyimide formation

A diffusion-limited kinetic model was developed to describe the imidization of one-step polythioetherimide formation based on an endgroup diffusion model. The changes of conversion and viscosity during the imidization were monitored with thermogravimetric analysis and dynamic stress rheometry, respectively. It was observed that the imidization rate began to decelerate after a fast early stage, whereas the viscosity in the system increased dramatically after a period of low value. Amic acid and imide formations concurrently take place in the one-step polyimide formation, but the formation of amic acid is much slower than that of imide and is the rate-limiting step of imidization. When a second-order kinetic model was used to describe the imidization, the effect of viscosity on the diffusion resistance of reactive groups needed to be included. In order to predict the change of viscosity during the imidization, the Lipshitz-Macosko model was modified and introduced into the diffusion-limited kinetic model by the Stokes-Einstein equation. The comparison of the modeled results with experimental data indicated that the diffusion-limited kinetic model and the modified Lipshitz-Macosko model were able to efficiently predict the changes of conversion and viscosity with temperature and time during the one-step polythioetherimide formation. (C) 2001 John Wiley & Sons, Inc.