A Ru(ii)-catalyzed C–H activation and annulation cascade for the construction of highly coumarin-fused benzo[a]quinolizin-4-ones and pyridin-2-ones

Abstract

A reaction involving a Ru(II)-catalyzed C–H activation and annulation cascade was successfully established for constructing coumarin-fused benzo[a]quinolizin-4-ones and pyridin-2-ones. In these constructions, an intriguing 6-6-6-6-6 pentacyclic coumarin-fused scaffold was formed as a result of two successive C–H bond activation/[4 + 2] annulation cascade in a one-pot operation with moderate to good yields, and a broad range of substrates were amenable to the reaction. More importantly, this work was the first time, to the best of our knowledge, that such complex 6-6-6-6-6 pentacyclic coumarin scaffolds were constructed using a successive Ru(II)-catalyzed C–H activation and annulation cascade. The resulting products were further transformed into two new interesting skeletons, and biological evaluations showed the highly fused products having good affinity for the ENL YEATS domain.