Nuevos heteropoliácidos como catalizadores heterogéneos en la producción sustentable de sulfóxidos y sulfonas

En el presente trabajo se describe la síntesis de HPA obtenidos en nuestro laboratorio por sustitución parcial de protones del H3PMo12O40 por aminas de diferente naturaleza estructural: quinoleina, cinconina y cinconidina, su caracterización y actividad catalítica en la oxidación selectiva de sulfuros a sulfóxidos y sulfonas. Esta reacción se estudió en diferentes condiciones de reacción: solventes de diferente polaridad (acetonitrilo y etanol), oxidantes (peróxido de hidrógeno acuoso, peróxido de t-butilo, percarbonato de sodio y un complejo de 1:1 de urea peróxido de hidrógeno) y las distintas solubilidades de los catalizadores preparados posibilitaron realizar la reacción tanto en medio homogéneo como heterogéneo. Por último, la influencia de la temperatura de reacción permitió modificar la selectividad de la reacción hacia la formación de sulfóxidos o sulfonas.Eje: Ciencia e ingeniería de materialesFacultad de Ciencias Exacta

Direct synthesis of N-methylurethanes from primary amines with dimethyl carbonate

The mechanism of the reaction between amines with dimethyl carbonate (DMC) has been investigated. Whereas in the absence of bases, they give methylation and carboxymethylation reactions without selectivity (BAl2 and B Ac2 mechanisms, respectively), in the presence of bases, the B Ac2 mechanism prevails. The carbamate already formed reacts further with DMC via the BAl2 mechanism to give the corresponding N-methyl derivative. Such pronounced double selectivity has been explained in terms of Pearson's Hard-Soft Acid-Base (HSAB) theory. Accordingly, N-methylcarbamates have been prepared from primary aliphatic and aromatic amines, either at reflux temperature of DMC (90 °C) or at 230 °C in autoclave. The reaction can be carried out in one step or through the isolation of the carbamate and the subsequent methylation reaction with DMC. This method is the direct synthesis, in high yield and selectivity, of secondary N-methylamines from the corresponding primary amines.Facultad de Ciencias Exacta

Uso de hardware libre en el laboratorio: soluciones de bajo costo

Se llama hardware libre a aquellos dispositivos de hardware cuyas especificaciones y diagramas esquemáticos son de acceso público, ya sea bajo algún tipo de pago, o de forma gratuita. La filosofía del software libre es aplicable a la del hardware libre, y por eso forma parte de la cultura libre.Centro de Investigación y Desarrollo en Ciencias Aplicada

Uso de hardware libre en el laboratorio: soluciones de bajo costo

Se llama hardware libre a aquellos dispositivos de hardware cuyas especificaciones y diagramas esquemáticos son de acceso público, ya sea bajo algún tipo de pago, o de forma gratuita. La filosofía del software libre es aplicable a la del hardware libre, y por eso forma parte de la cultura libre.Centro de Investigación y Desarrollo en Ciencias Aplicada

Vanadium-substituted Wells-Dawson potassium salt as catalyst for liquid phase oxidation of 1,4-dihydropyridine derivative

Dawson-type heteropolyoxometalate compounds (HPC) P2M18O62-6 (M= Mo, W) have received increasing attention in the catalytic field due to the combination of redox and acidic properties in the same structure. It has been proved that the introduction of vanadium into the Keggin framework is beneficial for redox Catalysis, shifting its activity from acid to redox-dominated. In this work we prepared and characterized vanadium (V) substituted Wells-Dawson heteropolysalt (WDKV). Fresh solid samples were characterized by 31P MAS-NMR, FTIR, SEM, XRD, TGA and Potentiometric titration measurements. Also, we performed the oxidation of a 1,4-dihydropyridine using WDKV as catalyst in acetonitrile media, with H2O2 as oxidant agent. The optimal procedure is the following: 1 mmol% of WDKV, a ratio 1,4-DHP: H2O2 (1:214) at reflux of acetonitrile. It must be noted that along all reactions, no secondary products were observed.Centro de Investigación y Desarrollo en Ciencias Aplicada

Heteropoliácidos de estructura tipo preyssler incluidos en una matriz de sílice como catalizadores en la eterificación de 5-hidroximetilfurfural

La síntesis de 5-butoximetilfurfural a partir de 5-hidroximetilfurfural y n-butanol se estudió usando Heteropoliácidos másicos H14NaP5W30O110(PW) y H14NaP5W29MoO110 (PWMo) e incluidos en sílice (PW@SiO2 y PWMo@SiO2). Para la optimización del proceso se analizó el efecto del disolvente, la carga de catalizador, la temperatura y el tiempo de reacción en la selectividad al éter. Se encontró que la conversión y selectividad al producto está relacionada con la fuerza ácida de los catalizadores. Se consiguen una conversión del 98% y una selectividad del 80% cuando se usa PMo@SiO2 como catalizador a 373 K. La reacción optimizada se extrapoló a una serie de alcoholes alifáticos y aromáticos obteniendo rendimientos aceptables. Estos resultados demuestran que los catalizadores derivados de Heteropoliácidos tipo Preyssler son buenos candidatos para la síntesis de éteres de 5-hidroximetilfurfural bajo condiciones suaves de reacción.Universidad Nacional de La Plat

Direct synthesis of N-methylurethanes from primary amines with dimethyl carbonate

The mechanism of the reaction between amines with dimethyl carbonate (DMC) has been investigated. Whereas in the absence of bases, they give methylation and carboxymethylation reactions without selectivity (BAl2 and B Ac2 mechanisms, respectively), in the presence of bases, the B Ac2 mechanism prevails. The carbamate already formed reacts further with DMC via the BAl2 mechanism to give the corresponding N-methyl derivative. Such pronounced double selectivity has been explained in terms of Pearson's Hard-Soft Acid-Base (HSAB) theory. Accordingly, N-methylcarbamates have been prepared from primary aliphatic and aromatic amines, either at reflux temperature of DMC (90 °C) or at 230 °C in autoclave. The reaction can be carried out in one step or through the isolation of the carbamate and the subsequent methylation reaction with DMC. This method is the direct synthesis, in high yield and selectivity, of secondary N-methylamines from the corresponding primary amines.Facultad de Ciencias Exacta

A study of the temperature effect on Hantzsch reaction selectivity using Mn and Ce oxides under solvent-free conditions

In this communication, four materials (CeO2, CeO2(Cu), MnOx, and MnOx(Cu))were prepared, characterized and tested as catalysts, in solvent-free conditions, for the multicomponent Hantzsch reactions to obtain alternatively the 1,4-dihydropyridine or 2-phenylpyridine depending on the reaction conditions. 1,4-Dihydropyridine 4 was the main product formed at 80 °C (76%), and 2-phenylpyridine 7 was the main product at 40 °C (91%), in oxidant-free conditions, using CeO2 catalyst. It is the first report that shows that, not only the temperature but also the nature of the catalyst may change the product selectivity in Hantzsch reactions.Centro de Investigación y Desarrollo en Ciencias Aplicada

Green Synthesis of Pyrrole Derivatives

Pyrroles are organic cyclic compounds with an extensive and fascinating chemistry. These compounds have a wide structural variety and are an important basis in technological development as they can be used as drugs, dyes, catalysts, pesticides, etc. Therefore, the production of these heterocyclic compounds by efficient clean methodologies is a great achievement in contemporary chemistry. In this paper, we show recent green procedures in the synthesis of pyrrole derivatives, such as Hantzsch, Knorr and Paal-Knorr syntheses, as well as new eco-friendly synthetic procedures with high efficiency and low environmental impact.Centro de Investigación y Desarrollo en Ciencias Aplicada

An Efficient K2CO3-Promoted Synthesis of 1-Bromo-2-aryloxyethane Derivatives and Evaluation of Larval Mortality against Aedes aegypti

The influences of reaction parameters on the etherification of phenols to obtain 1-bromo-2-aryloxyethane derivatives were evaluated. The compounds were prepared by direct etherification of phenols with 1,2-dibromoethane using anhydrous K2CO3 and acetonitrile as solvent reaction, at 80°C, in a reaction time of 6 h. Under these conditions, excellent yields (71%-94%) were obtained, with low yields of secondary products. The anhydrous K2CO3 was recycled by simple filtration, dried in vacuum, and reused. The compounds were characterized by conventional spectral data (MS and NMR). Larvicidal activity results showed a 100% larval mortality after 24-hour exposure to the compound 1-(2-bromoethoxy)-2-phenylbenzene.Facultad de Ciencias Agrarias y ForestalesCentro de Investigación y Desarrollo en Ciencias Aplicada