The presence of the phenanthridinone core in natural products and biologically active compounds has encouraged research on more efficient approaches to such valuable tricyclic framework.[1] Due to the lack of transmetallating agents and the atom-economy implied, palladium-catalyzed direct arylation is an appealing alternative for the ring closure step. However, the relative high amount of the catalyst employed may become a serious drawback from a practical view.[2] In this context, we wish to present the application of a palladacyclic complex to this reaction and the significant reduction of the catalytic amount achieved (0.05 mol%) in the successful preparation of a series of phenanthridinone derivatives.
[1] Bhakuni, B. S.; Kumar, A.; Balkrishna, S. J.; Sheikh, J. A.; Konar, S.; Kumar, S. Org. Lett. 2012, 14, 2838-2841.
[2] Rousseaux, S.; Gorelsky, S. I.; Chung, B. K. W.; Fagnou, K. J. Am. Chem. Soc. 2010, 132, 10692-10705.