Uso de catalisadores de cobre na síntese one-pot de 4-selenopirazóis

Abstract

This work describes a synthetic methodology to obtain 1,3,5-triaryl-4(organoselanyl)-1H-pyrazoles through cyclocondensation reactions followed by a selenization catalyzed by copper/bipyridine. A direct selenization reaction of the CH bond of 1,3,5-triaryl-1H-pyrazoles was developed through the reaction of arylhydrazines 1, chalcones 2 and diorganoyl diselenides 3, using a catalytic amount of copper/bipyridine (10 mol%) in acetic acid as a solvent at reflux temperature it was possible to achieve excellent results. This methodology proved to be simple and efficient to provide a wide reaction scope of 1,3,5triaryl-4-(organoselanyl)-1H-pyrazoles with moderate to good yields (Scheme 1).

Following the same line of research to obtain pyrazoles functionalized with an organic selenium group, another method was described to obtain 4- ix organoselanyl-1H-pyrazoles 4p-y using a catalyst alginate-based copper. In this study, 4-organoselanyl-1H-pyrazoles 4p-y were synthesized through the cyclocondensation reaction of diketones 5 and hydrazines 1, followed by the direct selenization reaction using diphenyl diselenide 3 and copper Alginate II catalysis. Through heterogeneous catalysis of copper alginate, dimethylsulfoxide (DMSO) as solvent at a temperature of 100 °C, the 4p-y products were obtained with yields ranging from moderate to excellent (Scheme 2). In addition, the catalyst reuse study was carried out, which proved to be efficient until the 3rd consecutive use.