Síntese de 3-organocalcogeno-benzo[b]furanos via reações de ciclização de 2-alquinil-fenóis mediadas por cobre

Abstract

This work describes the development of new approach for the synthesis of 3- organochalcogen-benzo[b]furans via CuI- promoted intramolecular cyclization of 2-alquinyl-phenols. Firstly, the 2-phenylethynyl-phenol was prepared by palladium catalyzed Sonogashira cross coupling reaction of 2-iodo-phenol and phenylacetylene. The 2-phenylethynyl-phenol was then used as standard substrate for the optimization studies, in order to determine an optimal cyclization condition to obtain the 2-phenyl-3-phenylselenyl-benzo[b]furan. Reaction parameters such as temperature, solvent, base, atmosphere and stoichiometry were tested and the results showed that best yield for the expected 2-phenyl-3- phenylselenyl-benzo[b]furan was obtained by using the 2-phenylethynyl-phenol (0.25 mmol), CuI (1.5 equiv), (PhSe) 2 (1.1 equiv), DMSO (3 mL) as solvent under ambient atmosphere and temperature (air; 25 °C). Using this cyclization method, the desired benzo[b]furan derivative could be isolated in 72% yield, under mild reaction conditions.