Síntese e aplicação de disselenetos derivados da piridina

Abstract

In the present work, a synthetic methodology was developed for the preparation of bis(2-pyridine)diselenides 3a-d by the reaction of different 2-chloropiridines 2a-d activated by p-TsOH.H2O with nucleophilic selenium species.The reaction was carried out by reducing elemental selenium with NaBH4 in PEG-400 as solvent, followed by the addition of 2-chloropyridine 2 previously activated by the acid. In this study, the reaction was shown to be especially effective in acidic condition and allowed the synthesis of bis(3-amino-2-pyridine)diselenides 3b-d, which has not been widely used in the literature until the present moment.The bis(3-amino-2-pyridine)diselenide 3b in the presence of different aldehydes was used for the synthesis of 2-aryl-[1,3]selenazolo[5,4-b]pyridines 5ad. This reaction was promoted by KOH in PEG-400 and the products 5a-d were obtained in yields ranging from 25 to 53%. In addition, the diselenide 3a proved to be efficient against nucleophilic substitution reactions. When tosylate 6 derived from glycerol was used the product 7 was isolated in 96% yield.xii The diselenide 3b was also used in aliphatic nucleophilic substitution reactions with different electrophilic reagents, which proved to be a good synthetic substrate for obtaining several organic selenides previously unpublished in the literature. Further, the reaction between the diselenide 3b and the 2-bromoacetophenone 17 produce compound 19 using NaBH4. In the of Rongalite®, the cyclization product 18 is obatined All products were identified and characterized by analyzes such as: 1H and 13C nuclear magnetic resonance spectroscopy; low and high resolution mass spectrometry and, x-ray diffraction in single crystal.