Selenilação de 2-arilimidazo[1,2-a]piridinas promovida por luz visível utilizando ácidos arilselenínicos

Abstract

In the present work, an alternative and mild method was developed for the synthesis of 2-aryl-3-(arylselanyl)imidazo[1,2-a]pyridines promoted by visible light. The synthetic strategy described to obtain these compounds involves the proportioning of arylseleninic acid, in which the reagents diphenyl diselenide generated from the decomposition of arylseleninic acid and arylseleninic acid have the same chemical element (selenium) with a different oxidation state and generate products with a different oxidation state to that of the reagents. The reaction consists of an electrophilic aromatic substitution of different 2-arylimidazo[1,2-a]pyridines and electrophilic selenium species generated in situ, under irradiation with blue LEDs (50 W) and using water as solvent. Thirteen products were obtained with yields from low to moderate (23-75%) in reaction times of 24 to 48 h. Furthermore, the developed method proved to be efficient when increasing the reaction scale (from 0.25 mmol to 2.5 mmol), which provided the desired product in 70% yield (0.61 g) after 24 h of reaction, demonstrating the applicability of this method in preparative scale. The presented method does not require the use of metals, oxidants and heating, in addition to producing as by-products only water and diaryl diselenide, which can be recovered and reused to obtain arylseleninic acid.