Synthesis of N-substituted benzo[c][1,7]- and benzo[c][1,8] phenanthrolin-(5H)-6-ones through a Pd-mediated Suzuki–Miyaura heteroaryl-aryl coupling reaction

In the course of the search for non-camptothecin topoisomerase I inhibitors we have undertaken the synthesis of N-substituted benzo[c][1,7]- and benzo[c][1,8]phenanthrolinone derivatives. An intermolecular Suzuki–Miyaura heteroaryl-aryl coupling reaction was planned as the key step. Then a nitro reduction followed by a concomitant lactamization achieved the construction of the tetracycle structures. This methodology permitted a rapid and efficient elaboration of biologically potent compounds.