Síntese de 3-organoselanil-benzo[b]furanos via reações de ciclização de 2-Alquinil-fenois promovidas por CuI

Abstract

This work describes an alternative method for the synthesis of 3-organochalcogen- benzo[b]furans derivates through intramolecular cyclization reactions of 2-alkynyl- phenols promoted by copper iodide and diorganyl diselenides, allowing the synthesis of thirteen 3-organoselanyl-benzo[b]furan derivates ranging from 24 to 72% yields. The cyclization reactions were performed under ambient conditions and absence of base, advantages from an economic and operational point of view. The methodology proved be efficient using both diorganyl diselenides and 2-alkynyl-phenols bearing electron-donor, withdrawing and neutral groups, but it wasn’t efficient to use diorganyl disulfides and ditellurides. In aim to verify the synthetic applicability of the obtained heterocycles, the 2-phenyl-3-phenylselanyl-benzo[b]furan was submitted to lithium-calcogen exchange reactions, allowing the synthesis of 2-phenyl- benzo[b]furan and 2-phenyl-3-benzoyl-benzo[b]furan in yields of 65 and 73%, respectively, and the bromination reaction to form 3,5-dibromo-phenylbenzo[b]furan in yield of 63%.