Synthesis of YAP nanopowder by a soft chemistry route

Polycrystalline fine powder of YAlO(3) (YAP) was synthesized by the modified polymeric precursor method. A preliminary gradual pyrolytic decomposition under nitrogen flux was crucial in the removal process of organic residues to avoid the formation of molecular level inhomogeneities. YAP single phase was crystallized at temperatures between 950 degrees C and 1000 degrees C using chemically homogeneous ball-milled amorphous particles and very fast heating rates, corresponding to the lowest synthesis temperature of pure YAP nanopowder by soft chemistry routes. (C) 2009 Elsevier Ltd. All rights reserved.

Vanadium Pentoxide Nanostructures: An Effective Control of Morphology and Crystal Structure in Hydrothermal Conditions

A systematic study was made of the synthesis of V(2)O(5)center dot nH(2)O nanostructures, whose morphologies, crystal structure, and amount of water molecules between the layered structures were regulated by strictly controlling the hydrothermal treatment variables. The synthesis involved a direct hydrothermal reaction between V(2)O(5) and H(2)O(2), without the addition of organic surfactant or inorganic ions. The experimental results indicate that high purity nanostructures can be obtained using this simple and clean synthetic route. Oil the basis of a study of hydrothermal treatment variables such as reaction temperature and time, X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) revealed that it was possible to obtain nanoribbons of the V(2)O(5)center dot nH(2)O monoclinic phase and nanowires or nanorods of the V(2)O(5)center dot nH(2)O orthorhombic phase. Thermal gravimetric analysis (TGA) shows also that the water content in the Structure call be controlled at appropriate hydrothermal conditions. Concerning the oxidation state of the vanadium atoms of as-obtained samples, a mixed-valence state composed of V(4+) and V(5+) was observed ill the V(2)O(5)center dot nH(2)O monoclinic phase, while the valence of the vanadium atoms was preferentially 5+ in the V(2)O(5)center dot nH(2)O orthorhombic phase. The X-ray absorption near-edge structure (XANES) results also indicated that the local structure of vanadium possessed a higher degree of symmetry in the V(2)O(5)center dot nH(2)O monoclinic phase.

Convergent synthesis and cruzain inhibitory activity of novel 2-(N `-benzylidenehydrazino)-4-trifluoromethyl-pyrimidines

To search for new cruzain inhibitors, the synthesis of a series of novel 2-(N`-benzylidenehydrazino)-4-trifluoromethyl-pyrimidines in a convergent manner is presented. The cruzain inhibitory activity of some of these compounds was evaluated and a binding model was proposed. All derivatives tested were active and the most significant inhibitory effect (80% at 100 mu M) and IC(50) value (85 mu M) were obtained from the 2-(N`-4-chloro-benzylidenehydrazino)-4-trifluoromethyl-pyrimidine. Although further structural optimization to improve solubility is necessary, the molecular docking studies suggest that these inhibitors occupy the S2 pocket without irreversible enzyme inactivation, through hydrophobic interactions, thus, indicating a desirable mode of interaction for the design of novel inhibitors. (C) 2008 Elsevier Ltd. All rights reserved.

Rhodium-catalyzed carbonylation of allylaminoalcohols: Catalytic synthesis of N-(2-hydroxy-alkyl)-gamma-lactams and bicyclic oxazolidines

Gamma-lactams and bicyclic oxazolidines are important structural frameworks in both synthetic organic chemistry and related pharmacological fields. These heterocycles can be prepared by the rhodium-catalyzed carbonylation of unsaturated amines. In this work, allylaminoalcohols, derived from the aminolysis of cyclohexene oxide, styrene oxide, (R)-(+)-limonene oxide, and ethyl-3-phenyl-glicidate, were employed as substrates. These allylaminoalcohols were carbonylated by employing RhClCO(PPh3)(2) as a precatalyst under varying CO/H-2 mixtures, and moderate to excellent yields were obtained, depending on the substrate used. The results indicated that an increase in the chelating ability of the substrate (-OH and -NHR moieties) decreased the conversion and selectivity of the ensuing reaction. Additionally, the selectivity could be optimized to favor either the gamma-lactams or the oxazolidines by controlling the CO/H-2 ratio. A large excess of CO provided a lactam selectivity of up to 90%, while a H-2-rich gas mixture improved the selectivity for oxazolidines, resulting from hydroformylation/cyclization. Studies of the reaction temperature indicated that an undesirable substrate deallylation reaction occurs at higher temperature (>100 degrees C). Further, kinetic studies have indicated that the oxazolidines and gamma-lactams were formed through parallel routes. Unfortunately, the mechanism for oxazolidines formation is not yet well understood. However, our results have led us to propose a catalytic cycle based on hydroformylation/acetalyzation pathways. The gamma-lactams formation follows a carbonylation route, mediated by a rhodium-carbamoylic intermediate, as previously reported. To this end, we have been able to prepare and isolate the corresponding iridium complex, which could be confirmed by X-ray crystallographic analysis. (C) 2008 Elsevier B.V. All rights reserved.

On the synthesis and structures of the complexes [RuCl(L)(dppb)(N-N)]PF(6) (L = CO, py or 4-NH(2)py; dppb=1,4-bis(diphenylphosphino)butane; N-N=2,2 `-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl(2)-Ru-pz-RuCl(2)(CO)(dppb)] (pz = pyrazine)

The ""Ru(P-P)"" unit (P-P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl(2)Ru-pz-RuCl(2)(CO)(dPPb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N-N)]PF(6) (N-N = diimine). Complexes with the formula (RuCl(py)(dppb)(N-N)]PF(6) were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl(2)(dppb)(N-N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and (31)P{(1)H)} NMR spectroscopy, cyclic voltammetry and X-ray crystallography. (C) 2010 Elsevier Ltd. All rights reserved.

Negishi cross-coupling of organotellurium compounds: synthesis of biaryls, aryl-, and diaryl acetylenes

A functional group tolerant palladium-catalyzed Negishi coupling of diaryl tellurides with organozinc has been developed. This methodology permits efficient preparation of biaryls, aryl acetylenes and diaryl acetylenes in moderate to good yields. A preliminary study to gain further insight into the reaction was performed using in situ ReactIR technology. (C) 2011 Elsevier Ltd. All rights reserved.

A large-scale synthesis of enantiomerically pure gamma-hydroxy-organochalcogenides

Enantiomerically pure (R)- and (S)-gamma-hydroxy-organochalcogenides are prepared using poly-[R]-3-hydroxybutanoate (PHB) as the starting material. (C) 2009 Elsevier Ltd. All rights reserved.

Biotransformations on organic selenides and tellurides: synthetic applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

(+)- and (-)-Mutisianthol: First Total Synthesis, Absolute Configuration, and Antitumor Activity

The first synthesis of the natural product (+)-mutisianthol was accomplished in 11 steps and in 21% overall yield from 2-methylanisole. The synthesis of its enantiomer was also performed in a similar overall yield. The absolute configuration of the sesquiterpene (+)-mutisianthol was assigned as (1S,3R). Key steps in the route are the asymmetric hydrogenation of a nonfunctionalized olefin using chiral iridium catalysts and the ring contraction of 1,2-dihydronaphthalenes using thallium(III) or iodine(III). The target molecules show moderate activity against the human tumor cell lines SF-295, HCT-8, and MDA-MB-435.

Synthesis, characterization and adsorption properties of porous mixed valent diruthenium(II,III)-terephthalate and diruthenium(II,III)-adipate polymers

Two porous mixed valent diruthenium(II,III)-dicarboxylate compounds have been prepared and characterized by spectroscopic methods, X-ray diffraction and thermogravimetry. Crystalline solids of [Ru(2)(tere)(2)Cl] center dot 3.5H(2)O (tere=terephthalate) and [Ru(2)(adip)(2)Cl] center dot 1.5H(2)O (adip=adipate) consist of extended chains in which polymeric layers of multiply metal-metal bonded [Ru(2)](5+) cores are bridged by dicarboxylate ligands in paddlewheel type geometries. Units of [Ru(2)(dicarboxylate)(2)](n)(+) are linked by axial bridging chloride ions generating three-dimensional networks. The polymers loose non-bonded water molecules at low temperatures but do not undergo thermal decomposition below 280-300 degrees C. Both of compounds exhibit high BET surface areas, [Ru(2)(tere)(2)Cl]: 235 m(2) g(-1) and [Ru(2)(adip)(2)Cl]: 281 m(2) g(-1), and occlude similar numbers of mol of N(2) per mol of metal. The terephthalate ligand generated an organized structure with supermicropores (total pore size of 0.24 cm(3) g(-1)) while the adipate ligand led to a mesoporous structure (total pore sizes of 0.47 cm(3) g(-1)) for the corresponding diruthenium(II,III)-dicarboxylate polymers. (c) 2008 Elsevier B.V. All rights reserved.

Hydrochalcogenation of activated olefines. Synthesis of functionalized dialkylchalcogenides

Alkanethiols, selenols and tellurols are generated in situ by reaction of elemental sulfur, selenium and tellurium with commercial alkyllithiums, followed by reaction with deoxygenated water. The alkanechalcogenols react in situ with activated ole. ns in a Michael- type addition reaction. (c) 2008 Elsevier B. V. All rights reserved.

First chemoenzymatic synthesis of organoselenium amines and amides

A series of organoselenium amines have been synthesized and submitted to the enzymatic kinetic resolution by acetylation mediated by CAL-B (Novozym 435) to give the corresponding chiral amides in an enantiomerically pure form. After evaluating the appropriate lipase, solvent, temperature,and lipase/substrate ratio in the kinetic resolution, the chiral organoselenium amides were obtained with enantiomeric excess of up to 99%. (C) 2008 Elsevier Ltd. All rights reserved.

A selective conductive polymer-based sensor for volatile halogenated organic compounds (VHOC)

A novel poly(p-xylylene), PPX, derivative bearing alkoxyphenyl side groups was electrochemically synthesized in 87% yield. The polymer, poly(4`-hexyloxy-2,5-biphenyleneethylene) (PHBPE), presented a fraction (92%) soluble in common organic solvents. It showed to be thermally resistant up to 185 degrees C. UV-vis analysis revealed an E-gap of 3.5 eV Gas sensors made from thin films of 10-camphorsulfonic acid-doped PHBPE deposited on interdigitated electrodes exhibited significant changes in electrical conductance upon exposure to five VHOCs: 1,2-dichloroethane, bromochloromethane, trichloromethane, dichloromethane and tetrachloromethane. The conductance decreased after exposure to tetrachloromethane and increased after exposure to all the other VHOCs. Three-dimensional plots of relative response versus time of half response versus time of half recovery showed good discrimination between the five VHOCs tested. (c) 2008 Elsevier B.V. All rights reserved.

Room Temperature, Metal-Free Synthesis of Diaryl Ethers with Use of Diaryliodonium Salts

A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky ortho-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives, and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in the pharmaceutical industry.

Palladium-catalyzed oxidative homocoupling of potassium alkenyltrifluoroborates: synthesis of symmetrical 1,3-dienes

Herein, we describe a convenient method for the synthesis of symmetrical 1,3-dienes employing an oxidative palladium-catalyzed homocoupling of potassium alkenyltrifluoroborates providing products in good yields relative to existing methodologies. This is the first report of a cross-dimerization of potassium alkenyltrifluoroborates. (C) 2009 Elsevier Ltd. All rights reserved.