Synthesis of thieno[2,3-h]-/[3,2-h]quinolines and thieno[2,3-f] 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.