Showing papers by "J. Carlos Menéndez published in 2006"
TL;DR: In this article, the solid-state reaction between anilines and phenacyl bromides in the presence of an equimolecular amount of sodium bicarbonate gives N-phenacylanilines.
Abstract: The solid-state reaction between anilines and phenacyl bromides in the presence of an equimolecular amount of sodium bicarbonate gives N-phenacylanilines. Microwave irradiation of mixtures of these compounds with anilinium bromides at 540 W for 45-60 s provides a mild, general, and environmentally friendly method for the synthesis of 2-arylindoles in 50-56% overall yields. A one-pot variation of the method, involving irradiation of 2:1 mixtures of anilines and phenacyl bromides, was also developed, allowing a simplified experimental procedure and leading to improved yields (52-75%).
12 citations
7 citations
TL;DR: In this paper, a general, efficient and environmentally friendly procedure for the synthesis of 2,5-piperazinediones is described, involving the microwave irradiation of N-Boc dipeptide esters.
Abstract: A general, efficient and environmentally friendly procedure for the synthesis of 2,5-piperazinediones is described, involving the microwave irradiation of N-Boc dipeptide esters.
5 citations
TL;DR: In this article, the solid-state reaction between anilines and phenacyl bromides in the presence of an equimolecular amount of sodium bicarbonate gives N-phenacylanilines.
Abstract: The solid-state reaction between anilines and phenacyl bromides in the presence of an equimolecular amount of sodium bicarbonate gives N-phenacylanilines. Microwave irradiation of mixtures of these compounds with anilinium bromides at 540 W for 45-60 s provides a mild, general, and environmentally friendly method for the synthesis of 2-arylindoles in 50-56% overall yields. A one-pot variation of the method, involving irradiation of 2:1 mixtures of anilines and phenacyl bromides, was also developed, allowing a simplified experimental procedure and leading to improved yields (52-75%).
5 citations
TL;DR: Microwave irradiation in the presence of palladium acetate and traces of dimethylformamide allows the fast and efficient cyclodehydrogenation of diphenylamines into carbazoles as discussed by the authors.
Abstract: Microwave irradiation in the presence of palladium acetate and traces of dimethylformamide allows the fast and efficient cyclodehydrogenation of diphenylamines into carbazoles. The scope of the microwave-assisted reaction is broader than that of the one using conventional conditions in that it allows the preparation of oxygenated carbazoles without apparent loss in yield. The applicability of the method to the preparation of carbazole alkaloids has been demonstrated by the development of a total synthesis of murrayafoline A, which proceeds in 50% overall yield from commercially available materials and is the shortest and most efficient route for the preparation of this alkaloid to date.
5 citations
01 Jan 2006
TL;DR: The parametro σ of Hammett as discussed by the authors is one of the principal parametros relacionados with el caracter donador o aceptor electronico of un sustituyente presente en the molecula de un farmaco.
Abstract: La constante de disociacion acida, que describe la ionizacion de compuestos en disolucion acuosa, es una propiedad fisica fundamental de los farmacos. Es frecuente encontrar diferencias en la solubilidad y por tanto en la absorcion, biorreactividad y toxicidad, cuando se comparan las propiedades de las especies neutras e ionizadas. En la bibliografia no siempre se encuentran valores de pKa determinados experimentalmente, por lo que es necesario calcularlos. Uno de los principales parametros relacionados con el caracter donador o aceptor electronico de un sustituyente presente en la molecula de un farmaco es el parametro σ de Hammett, que se define a partir de los valores de pKa, del acido benzoico y sus derivados, como se vera mas adelante. Aunque este parametro se introdujo en un contexto fisicoquimico, es muy importante tambien en el ambito de la Quimica Farmaceutica, ya que uno de los objetivos del diseno de farmacos es la busqueda de relaciones cuantitativas entre la estructura quimica y la actividad biologica (QSAR). Este objetivo requiere disponer de parametros (descriptores) que permitan expresar de forma cuantitativa las variaciones de ciertas propiedades fisicoquimicas al modificar la estructura. Hammett propuso que cada grupo funcional unido a la molecula del acido benzoico produce un efecto predecible sobre su acidez. Para cuantificarlo, definio para cada sustituyente y cada posicion una constante de sustituyente σX, de la siguiente forma:
1 citations