The synthesis of 4‐trifluoromethyl‐2‐methyl[phenyl]pyrimidines and the corresponding tetrahydro derivatives from the cyclo‐condensation reaction of β‐alkoxyvinyl trifluoromethyl ketones 1a‐d with acetamidine or benzamidine hydrochloride, is reported. For the cyclo‐condensation of 1a‐d with acetamidine and benzamidine hydrochloride, two methods were tested: 1 M solution of sodium hydroxide (method A) and sodium alkoxide/alcohol (method B). Depending on the structure of the β‐alkoxyvinyl trifluoromethyl ketones and the reactions conditions, pyrimidines or tetrahydropyrimidines or a mixture of both compounds were obtained.

Recebido em 5/8/09; aceito em 16/11/09; publicado na web em 24/3/10 FATTY ESTER CONTENT DETERMINATION IN SOYBEAN METHYL BIODIESEL BY GAS CHROMATOGRAPHY USING ETHYL OLEATE AS INTERNAL STANDARD. A method for ester content determination in soybean methyl biodiesel was studied, using ethyl oleate as internal standard. A biodiesel sample was analyzed and had its purity estimated as 92.8%. Method accuracy was evaluated by comparison with the result obtained via EN14103, with a relative difference of 0.1%. Repetitivity and intermediate precision were estimated as 2 and 1.5%, respectively.

The stereoselective synthesis of novel multifunctionalized cyclopropanes from γ,δ-epoxy malonates and amines mediated by LiCl under mild conditions was carried out. This domino reaction involves the initial cyclopropanation via intramolecular ring-opening of γ,δ-epoxy malonates through the cooperative catalysis of LiCl (acting as a Lewis acid) and a Brønsted base (a primary or, in selected cases, a secondary amine). The sequential events consisted of lactonization and aminolysis of the lactone ring, which ultimately furnished cyclopropanecarboxamides with different substitution patterns in good isolated yields. In all cases, a quaternary stereogenic center could be perfectly assembled, with a single diastereoisomer being obtained. This method proceeds with high atom economy, is remarkably modular and operationally simple, and tolerates a variety of functional groups. The involvement of readily available starting materials, the broad scope, and the use of a sustainable solvent (methanol or ethanol) at ambient temperature make this domino process highly effective. A reaction mechanism is proposed on the basis of the experimental observations involving the preparation and reactivity of cyclopropylidene lactones as possible intermediates of the domino process.

No abstract

The synthesis of small spherical palladium(II) iodide nanoparticles is reported for the first time. The formation of the particles by ligand exchange, in the presence of poly(vinyl pyrrolidone) in aqueous medium at room temperature, was investigated by in situ time‐resolved synchrotron‐based SAXS and XANES/EXAFS analysis. These new nanomaterials exhibit a double catalytic role in an aryl alkenylation chemical reaction, working without a base or ligand, in aqueous milieu. There is strong experimental evidence to suggest that the mechanism follows a single‐electron transfer (SET) pathway with the participation of iodide as a radical promoter and the palladium atoms as activator of the alkene moiety. This new protocol could evolve into a broadly applicable radical reaction for the functionalization of alkenes.

Recebido em 2/2//06; aceito em 25/4/06; publicado na web em 30/8/06 SULFADIMETHOXYNE QUANTIFICATION IN MILK BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY. A method for HPLC determination of sulfadimethoxyne in milk is presented. The analyte isolation and concentration were performed by solidphase extraction through a C-8 cartridge, pre-conditioned with hexane, methanol and water and eluted with MeOH. The recovery determination was done with a spiked solution of 20, 50 or 100 μg L -1 . In this concentration range, the recovery was 83.2% with a RDS of 15.4%. For quantification, a Zorbax Eclipse XDB-C8 (4.6 mm x 150 mm, 5 μm), a mobile phase of MeCN: 0.01 mol L -1 KH 2 PO 4 aq. (1:4), and a variable wavelength detector (275 nm) were used.Keywords: sulfadimethoxyne; milk; HPLC. INTRODUÇÃOSulfonamidas, assim como outras classes de antibióticos, têm sido administradas ao gado leiteiro com objetivos terapêutico, profilático ou, ainda, como estimulante de crescimento. Uma conseqüência dessa prática é a ocorrência de resíduos desses medicamentos no leite, que, mesmo em quantidades traços, podem causar problemas de saú-de, como o aparecimento de reações tóxicas no consumidor ou um aumento da resistência de determinadas bactérias ao agente antimicrobiano. Segundo a Agência Nacional de Vigilância Sanitária (ANVISA), são alvo de controle sulfadimetoxina (1) sulfatiazol (2) e sulfametazina (3), tendo sido estabelecido um limite máximo de resí-duo (LMR) de 100 μg kg -1 para o somatório das três sulfonamidas 1 . A Figura 1 apresenta as estruturas químicas das três sulfas.A Associação dos Químicos Analíticos Oficiais (AOAC) descreve um método para quantificação de sulfas em leite 2 que inclui os compostos 1-3. As sulfas são isoladas por extração líquido-líquido com clorofórmio/acetona (2:1) e analisadas por cromatografia líquida de alta eficiência (CLAE) em coluna C-18, tendo misturas de MeOH e KH 2 PO 4 aq. 0,1 mol L -1 como eluente. O método, entretanto, não possibilita a quantificação simultânea das três sulfas e oferece baixa recuperação para sulfadimetoxina (1) e sulfatiazol (2). Além disso, apresenta os inconvenientes comuns à extração líquido-líquido, como formação de emulsões e grande consumo de solventes.Alternativamente, a extração em fase sólida (EFS) tem sido bastante empregada em determinações semelhantes. Entre outras vantagens, a EFS pode levar a uma diminuição de tempo de preparo de amostra, bem como do volume total de solvente consumido no procedimento. Pode, ainda, proporcionar uma concentração do analito de interesse e a eliminação de interferentes 3,4 . De fato, há alguns relatos na literatura sobre o uso da EFS no isolamento de sulfas em leite 5-8 , embora o método tenha sido, algumas vezes, criticado por sua eventual falta de reprodutibilidade ou baixa capacidade de recuperação 7,8 . Além da EFS em cartuchos, também a dispersão da matriz na fase sólida tem sido relatada 7-10 . Como alternativa à fase sólida C-18 9,10 , outras fases como os trocadores de íons vêm encontrando emprego 5,6,11 .Com relação ao sistem...

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We describe herein a general method for the controlled Heck arylation of allylated malonates. Both electron-rich and electron-poor aryldiazonium salts were readily employed as the aryl-transfer agents in good yields and in high chemo-, regio-, and stereoselectivity without formation of decarboxylated byproducts. Reaction monitoring via ESI-MS was used to support the formation of chelated Pd species through the catalytic cycle. Additionally, some Heck adducts were successfully used in the total synthesis of pharmacologically active γ-lactones.