“Síntese de 3-selanil-1H-indóis e 3-selanilimidazo[1,2-a]piridinas promovida por ultrassom

Abstract

The development of versatile and simple protocols for accessing 3-selanyl-1H indoles 3 and 3-selanylimidazo[1,2-a]pyridines 3’ is essential to allow further studies on their chemical and pharmacological properties. In this sense, two works were developed. The first study describes the regioselective selenation of indoles 1 and imidazopyridines 1’ assisted by ultrasound, using diorganyl diselenide 2 and CuI/SeO2 as catalytic system in DMSO (Part 1, Scheme 1). By this method, 20 examples were synthesized, with yields between 57-96%, showing the wide variation of the reaction scope, and in short reaction times, of 15 to 60 min. The use of selenium dioxide had a positive effect, increasing the yield while decreasing reaction times, making this protocol a simple, efficient and fast alternative to the current methods. The second study involves the one-pot synthesis of 3-selanylimidazo[1,2 a]pyridines 3’ (Part 2, Scheme 1). This study was also carried out under sonication through a two-step, one-pot procedure, where in the first one, 2 bromoacetophenones 4 were reacted with 2-aminopyridine 5, in the presence of K2CO3 and using PEG-400 as green solvent, delivering imidazo[1,2-a]pyridine nucleus 1’. After that, a direct selenation was carried out using diorganyl diselenide 2 in the presence of CuSO4/KI. A total of 17 different 3-selanylimidazopyridines 3’ were obtained in a yield range of 5% to 95%, after 1 to 2 h of reaction. The one-pot method developed was robust for a diversity of diorganyl diselenides 2 and 2 bromoacetophenones 4.