Synthesis of some pyrimido[4′,5′:4,5]thieno[2,3‐b]quinolines and related heterocycles

Several thieno[2,3‐b]quinolines 6a‐i have been synthesized. These compounds were used as key intermediates in the synthesis of oxazino[4′,5′:4,5]thieno[2,3‐b]quinoline 8, pyrimido[4′,5′:4,5]‐thieno[2,3‐b]quinolines 9–12, triazino[4′,5′:4,5]thieno[2,3‐b] quinolines 14 and imidazo[4′,5′:4,5]‐thieno[2,3‐b]quinolines 17.