Direct access to benzofuro[2,3-b]quinoline and 6H-chromeno[3,4-b]quinoline cores through gold-catalyzed annulation of anthranils with arenoxyethynes and aryl propargyl ethers

This work reports a facile annulation of anthranils with aryloxyethynes or aryl propargyl ethers to construct useful benzofuro[2,3-b]quinoline and 6H-chromeno[3,4-b]quinoline frameworks, respectively; these heterocycles are not readily available from literature methods despite their biological significance. This high atom- and step-economy strategy is highlighted by a broad substrate scope. The reaction mechanism is proposed to proceed through sequential cyclizations among the oxyaryl group, gold carbene and benzaldehyde of the α-imino gold carbene intermediates.