Gilber R. Rosa

Palladium nanoparticles supported in a polymeric membrane: an efficient phosphine-free “green” catalyst for Suzuki–Miyaura reactions in water

Palladium(0) nanoparticles supported on a polymeric membrane, CA/Pd(0), were found to be a highly efficient “dip catalyst” (heterogeneous catalyst) for Suzuki–Miyaura cross-coupling reactions. Iodo-, bromo- and electron-poor chloroarenes coupled with phenylboronic acid under eco-friendly conditions (i.e., phosphine-free and with water as the solvent) to give excellent yields. The CA/Pd(0) was prepared initially via the synthesis of Pd(0) by hydrogen decomposition of Pd(acac)2 dissolved in BMI·BF4 ionic liquid at 75 °C for 1.0 hour to yield a black suspension (nanoparticles with a diameter of 2.7 ± 0.4 nm). These nanoparticles were washed with acetone and dried under reduced pressure. The Pd(0) nanoparticles were subsequently added to a cellulose acetate solution with acetone to generate the CA/Pd(0) polymeric membrane. The CA/Pd(0) “dip catalyst” was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM).

NCP pincer palladacycle as a phosphine-free catalyst precursor for the Heck-Mizoroki coupling of aryl halides{

NCP pincer palladacycle 1 has been reported as an excellent catalyst precursor for the Suzuki–Miyaura reaction. Now, it’s properties have been evaluated in the Heck reaction. 1 is highly active for the coupling of ArI, ArBr and electron-poor ArCl with n-butyl acrylate showing limitations in the reaction of deactivated ArCl and sterically hindered olefins.

PdCl2 Immobilized in Polyacrylamide: a Low Cost and Eco-Friendly Catalyst for Suzuki-Miyaura Reactions

PdCl2 immobilized in polyacrylamide (PAM), named Pd/PAM, produced at an extremely low cost, was found to be an efficient catalyst for Suzuki-Miyaura cross-coupling reactions. Iodo- and bromoarenes may couple with phenylboronic acid under eco-friendly conditions (i.e., phosphine-free and with ethanol as the solvent) to give excellent product yields. Aryl chlorides, in contrast, were found to be unsuitable reagents in this context, yielding modest results. The recyclability of Pd/PAM is limited because of PdII leaching, which leaves only the base polymer on the surface after six runs. The Pd/PAM catalyst was initially prepared via the formation of a PAM hydrogel using an aqueous PdCl2 solution. After drying, the solid Pd/PAM was characterized by scanning electron microscopy (SEM), electron-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma optical emission spectrometry (ICP OES).

Miniprojeto para ensino de Química Orgânica Experimental baseado no acoplamento catalítico N-C promovido por micro-ondas

This paper describes a three-week mini-project for an Experimental Organic Chemistry course. The activities include N-C cross-coupling synthesis of N-(4-methoxyphenyl) benzamide in an adapted microwave oven by a copper catalyst (CuI). Abilities and concepts normally present in practical organic chemistry courses are covered: use of balances, volumetric glassware, separation of mixtures (liquid-liquid extraction and filtration), chromatographic techniques, melting point determination and stoichiometric calculations.

Miniprojeto para ensino de química geral experimental baseado na fermentação do caldo de cana-de-açúcar

This paper describes a five-week mini-project for a general chemistry laboratory course. Activities are included preparations of ethanol and sucrose solutions, calculation of concentrations, determination of densities with densimeters, sugarcane juice fermentation with CO2 capture in alkaline solution, distillation, and determination of amounts of ethanol and CO2 formed. Abilities and concepts normally present in practical general chemistry courses are covered: use of balances, volumetric glassware and densimeters, preparation of solutions, performing of dilutions, determination of solution densities, observation of chemical reactions, stoichiometric calculations, separation of mixtures, and titration.

Estratégias para estudo das correlações de energia livre em acoplamento aril-aril de Suzuki: elucidando ciclos catalíticos através da equação de Hammett

The present work deals with the study of the correlation of free-energy developed in a catalytic system for Suzuki coupling, by way of the Hammett equation. The system presents NCP pincer palladacycle 1 as a catalyst precursor, which proved to be very efficient in the coupling of various aryl boronic acids with aryl halides in previous studies. Thus, the article presented here intends to serve as a support for further investigations and clarifications relating to cross-coupling catalytic cycles.

EFFECTS OF SOLVENT, BASE, AND TEMPERATURE IN THE OPTIMISATION OF A NEW CATALYTIC SYSTEM FOR SONOGASHIRA CROSS-COUPLING USING NCP PINCER PALLADACYCLE

The optimisation of a new catalyst system using NCP pincer palladacycle 1 was investigated using the experimental design technique. NCP pincer palladacycle 1 was previously investigated in Suzuki-Miyaura and Heck-Mizoroki cross-couplings and found to be a highly efficient catalyst precursor. In this study, the effects of the type of base (K3PO4 or DABCO), solvent (DMF or dioxane) and reaction temperature (130 or 150 oC) in the second step on the reactional yield in Sonogashira cross-coupling were assessed using the two-factor design. The results showed that temperature is statistically significant in relation to the reaction yield.

SEASONAL VARIATION OF THE ESSENTIAL OIL OF Cabralea canjerana

The leaves of C. canjerana were collected in the town of Chapeco, Brazil, in July and November (2008) and January and April (2009), and a voucher specimen (SMDB 12.356) has been deposited in the Herbarium of the UFSM. The fresh leaves were submitted to hydrodistillation (4 h) to yield ca. 0.5% of oil. The oil was submitted to GC analysis in a Shimadzu (GCMS-QP2010 Plus) chromatograph equipped with a capillary fused silica column (30 m 0.25 m) coated with RTx-5MS. The injector and detector temperatures were 240 and 260C, respectively. He was used as carrier gas at a flow rate of 1 mL min –1 , injection was in the split mode (1:10), and the injection volume was 1 mg mL –1 of a solution containing oil in hexane. MS spectra were obtained using electron impact at 70 eV with a scan interval of 2.94 scan s –1 . The compound identification was based on a comparison of retention index with the same columns and mass spectra described [5, 6]. Retention indices (RI) have been obtained according to the method of Van den Dool relative to C7–C30 saturated n-alkane standards. Quantitative analyses of the chemical constituents was performed using a flame ionization detector (FID) and a Shimadzu (GC-2010) instrument under the same conditions and with the same column as reported for the GC-MS. The antimicrobial activity of the essential oil of C. canjerana was evaluated in vitro using the method of filter paper disc diffusion [7–9]. Fifty-seven compounds were identified in the essential oil of C. canjerana, showing only sesquiterpenes, especially oxygenated sesquiterpenes. The main component that showed a variation in concentration in different seasons was spathulenol (1); in spring time a lower concentration (10.8%) of this compound was found (Fig. 1). Spring, which is the season of fullest blossoming of C. canjerana, also showed the major compounds to be caryophyllene oxide (2) and -cadinol (3). These two compounds were found in oils from other seasons in lower concentrations. The oil collected in the autumn showed cubebol (6, 9.3%) and globulol (5, 9.8%). Cubebol was not found in the essential oil during the summer and winter seasons. The highest concentration of dihydroeudesmol (4) was found in summer but not found at all in autumn. The oil of C. canjerana was active against all bacteria tested. However, S. flexneri bacteria were less sensitive to the oil, only showing sensitivity to the oil collected in the spring. The bacteria most sensitive to the oil of C. canjerana were