A new approach based on multicomponent/domino combined reactions for the synthesis of γ-nitroesters promoted by a mixed aluminium-magnesium oxides derived from hydrotalcite-like material was developed. Different γ-nitroesters were synthesized in 15-95% yield using Meldrum's acid, aromatic aldehydes, nitromethane and different alcohols as reagents and solvents. The γ-aminobutyric acid derivatives, Phenibut and Baclofen, were prepared in 63 and 61% overall yield, respectively, through a two steps synthetic strategy. A mechanistic pathway was proposed based on the gas chromatography mass spectrometry (GC-MS) and electrospray ionization mass spectrometry (ESI-MS) experiments.

Uma série de novas pirazolinas N-acil trialometiladas derivadas de ésteres metílicos de ácidos graxos foi sintetizada por reação de ciclocondensação entre hidrazidas graxas e 4-alcóxi-1,1,1-trialometil-3-alquen-2-onas. Ciclizações eficientes e regioespecíficas catalisadas por BF3·MeOH levaram aos produtos desejados em rendimentos de bons a excelentes e alto grau de pureza.

A series of new fatty N-acyl trihalomethylated pyrazoline derivatives from fatty acid methyl esters was synthesized by the cyclocondensation of respective fatty hydrazides with 4-alkoxy-1,1,1-trialomethyl-3-alquen-2-ones. Efficient and regiospecific cyclizations catalyzed by BF3·MeOH gave the desired products in good to excellent yields and at high purity.

Resíduos de quatro agrotóxicos foram determinados durante um ano em águas de poços de uma área agrícola no Sul do Brasil. Os métodos para a separação, identificação e quantificação dos compostos incluíram cromatografia líquida de alta eficiência com detecção por arranjo de diodos (HPLC-DAD) e cromatografia líquida acoplada à espectrometria de massas (LC-ESI-MS/MS). Uma etapa de pré-concentração baseada na extração em fase sólida com cartuchos de 200 mg de C18 foi realizada. Todos os parâmetros analíticos ficaram de acordo com os limites sugeridos para a validação de métodos cromatográficos. Os limites de quantificação para o método, considerando um fator de pré-concentração de 250 vezes, foram 0,2 μg L-1 para todos os analitos por HPLC-DAD, 4,0 ng L-1 para o clomazona, carbofurano e tebuconazol e 40,0 ng L-1 para o 2,4-D por LC-ESI-MS/MS. Nas amostras de águas subterrâneas, o 2,4-D não foi detectado e o carbofurano, clomazona e tebuconazol apresentaram concentrações que variaram entre 0,25 e 10,40 μg L-1, 0,20 e 0,82 μg L-1, e 0,20 e 4,16 μg L-1, respectivamente. Os métodos mostraram-se adequados para a determinação de agrotóxicos em águas subterrâneas.

Residues of four pesticides in groundwaters were surveyed during one year in an agricultural area in southern Brazil. The methods for separation, identification and quantification of the compounds included high-performance liquid chromatography with diode array detection (HPLC-DAD) and liquid chromatography with electrospray interface tandem mass spectrometry (LC-ESI-MS/MS). A pre-concentration step based on solid-phase extraction with 200 mg C18 cartridges was applied. All the analytical parameters were within the limits suggested for the validation of chromatographic methods. The LOQs for the methods, considering the 250-fold pre-concentration step, were 0.2 μg L-1 for all pesticides by HPLC-DAD, 4.0 ng L-1 for clomazone, carbofuran and tebuconazole and 40.0 ng L-1 for 2,4-D by LC-ESI-MS/MS. In groundwater samples, 2,4-D was not detected, and carbofuran, clomazone and tebuconazole were detected in concentrations ranging from 0.25 to 10.40 μg L-1, from 0.20 to 0.82 μg L-1 and from 0.20 to 4.16 μg L-1, respectively. The methods proved to be adequate for the analysis of pesticides in groundwaters.

A adição de aliltrimetilsilano, promovida por TiCl4, a íons N-aciliminios cíclicos de 5- e 6-membros derivados do ácido (S)-(+)-mandélico, (1R,2S)-trans-2-fenil-1-cicloexanol e (1R,2S,5R)-8-fenilmentol ocorreu com baixas a moderadas razões diastereoisoméricas (1:1-6:1) e forneceu as respectivas amidas e carbamatos em bons rendimentos. A melhor diastereosseleção facial foi observada com o uso de (1R,2S,5R)-8-fenilmentol como auxiliar quiral. As amidas e carbamatos 2-substituídos foram convertidos nos alcalóides (S)- e (R)-propil pirrolidina e coniina com eficiente recuperação dos auxiliares quirais.

The TiCl4- promoted addition of allyltrimethylsilane to chiral 5- and 6-membered N-acyliminium ions employing (S)-(+)-mandelic acid, (1R,2S)-trans-2-phenyl-1-cyclohexanol and (1R,2S,5R)-8-phenylmenthol derivatives as chiral auxiliaries occurred with low to moderate diastereoisomeric ratios (1:1-6:1) to afford 2-substituted amides and carbamates in good yields. The best diastereoselection was observed with (1R,2S,5R)-8-phenylmenthol as the chiral auxiliary. The 2-substituted amides and carbamates were converted to the corresponding alkaloids (S)- and (R)-propyl pyrrolidine and coniine with efficient recovery of the chiral auxiliaries.