A facile synthesis of 3-substituted 2-amidobenzofurans and 2-amidobenzothiophenes via electrophilic cyclization reaction of o-anisole- and o-thioanisole-substituted ynamides with I2, NBS and NCS was developed. The products 3-iodo-2-amidobenzofurans were further transferred into 3-aryl-, 3-alkynyl, and 3-vinyl-2-amidobenzofurans via Pd-catalyzed reactions such as Suzuki–Miyaura and Sonogashira cross-coupling reactions and the Heck reaction.
Key words
2-amidobenzofurans - 2-amidobenzothiophenes - electrophilic cyclization - ynamide - cross-coupling reaction