Palladium catalysed regioselective arylation of indoles, benzofuran and benzothiophene with aryldiazonium salts

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Aryldiazonium tetrafluoroborates have been successfully employed in the direct and regioselective arylation of heteroaromatics such as indole, benzofuran and benzothiophene. The cationic aryl palladium intermediates derived from the aryldiazonium salts act as effective electrophiles in the process. These arylating reactions display operational simplicity and provide the arylated heterocycles regioselectively in moderate to excellent yields.2311193011935Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Solid phase microextraction fibers coated with sol-gel aminopropylsilica/polydimethylsiloxane: Development and its application to screening of beer headspace

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The preparation and applicability of solid phase microextraction (SPME) fibers coated with a sol-gel organically modified silica based on 3 -aminopropyltrimethoxysi lane and polydimethylsiloxane (APTMS/PDMS) are described here. Micrographs of the coated fibers revealed a rugous surface; the thickness of the coating was estimated to be less than 30 gm. The APTMS/PDMS fibers were tested with synthetic samples and compared to commercial fibers for headspace SPME analysis of beer. Extraction and desorption using the APTMS/PDMS fibers were faster, which is typical for sol-gel SPME fibers. For polar and semi-polar compounds on beer headspace, the extraction efficiencies of the APTMS/PDMS fiber were superior to those of conventional fibers. The APTMS/PDMS fiber was found to be capable of extracting a broad range of analytes, including highly polar acidic species such as organic acids.24911411146Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Expeditious Synthesis of the Marine Natural Products Prepolycitrin A and Polycitrins A and B through Heck Arylations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)New, efficient protocols for the syntheses of the marine natural products prepolycitrin A as well as polycitrins A and B were developed by employing the Heck-Matsuda arylation of maleic anhydride or dimethyl fumarate with aryldiazonium tetrafluoroborates. Both symmetrical and unsymmetrical 3,4-diarylmaleic anhydrides were easily and effectively prepared. Efficient bromination reactions that employed tribromoisocyanuric acid provided access to the polycitrin family of compounds. Under microwave irradiation in the presence of tyramine, the corresponding maleimides were obtained in high yields from the brominated 3,4-diarylmaleic anhydrides. This methodology provided for the concise synthesis of prepolycitrin A and the total syntheses of the marine alkaloids polycitrins A and B in overall yields of 37 and 47% from maleic anhydride and dimethyl fumarate, respectively.20133580048013Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [2011/23832-6

Preparation and characterization of a new sol-gel hybrid based tetraethoxysilane-polydimethylsiloxane as a stir bar extraction sorbent materials

A new tetraethoxysilane-polydimethylsiloxane (TEOS-PDMS) for use as sorbent of stir bar sorptive extraction (SBSE) towards two selected organophosphorus pesticides (OPPs) namely chlorpyrifos and malathion was successfully synthesized through sol-gel technology. Four different molar ratios of TEOS:PDMS (1:1, 2:1, 3:1 and 4:1) sol solutions were prepared and dipped coated onto the surface of a glass-encased stir bar. Extraction efficiency of the prepared coatings towards the two selected OPPs were compared. A number of factors have been found to greatly affect the characteristics and properties of a particular sol-gel coating. Hence, in this study, several sol-gel coating conditions have been optimized using the optimized molar ratio 3:1 TEOS:PDMS to obtain the best coating as the stationary phase for SBSE. The raw OH-TPDMS and TEOS were characterized using Fourier Transform Infrared Spectroscopy (FT-IR) and compared with spectra of the four different molar ratios of TEOS:PDMS. The FT-IR spectrum of TEOS:PDMS showed the co-polymerization between PDMS and hydrolyzed TEOS molecules demonstrating the formation of the hybrid network in the sol-gel hybrid material. Surface morphology of hybrid sol-gel TEOS-PDMS with optimized molar ratio of 3:1 TEOS:PDMS were examined using FE-SEM. The surface of the sol-gel coating seems to be rough and homogeneous. The more rough structure formed by the 3:1 molar ratio TEOS:PDMS provides enhanced surface area which in turn improved sample capacity or adsorption process