Synthesis of thieno[2,3-]-/[3,2-]quinolines and thieno[2,3-] quinolines by Brønsted acid mediated cycloisomerisation

Several thieno[2,3- h ]-/[3,2- h ]- and [2,3- f ]quinolines have been synthesised from 2,3-dihalogenated pyridines or -quinolines by site-selective Pd catalysed cross-coupling reactions and Brønsted acid mediated cycloisomerisations as the final key step. This newly developed synthetic strategy is used in a modular way to synthesize diverse regioisomeric derivatives, tolerates various functional groups, and proceeds with high selectivity, and the desired final products have been isolated in high overall yields. Several thieno[2,3- h ]-/[3,2- h ]- and [2,3- f ]quinolines have been synthesised from 2,3-dihalogenated pyridines or -quinolines by site-selective Pd catalysed cross-coupling reactions and Brønsted acid mediated cycloisomerisations as the final key step.