Ruthenium-Catalyzed Double C(sp(2))-H Functionalizations of Fumaramides with Alkynes for the Divergent Synthesis of Pyridones and Naphthyridinediones

Transition-metal-catalyzed C-H functionalization of aromatic secondary amides with alkynes mainly undergo C-H/N-H annulation but rarely undergo ortho-alkenylation. It is particularly challenging to selectively realize both oxidative annulation and ortho-alkenylation of aromatic secondary amides with alkynes in the transition-metal-catalysis. In this article, we synthesized fully-substituted 2-pyridones and 2,6-naphthyridine-1,5-diones via C(sp(2))-H functionalization of fumaramides for the first time. Under the Ru-catalysis, fumaramides and 1,2-diaryl ethynes first undergo C-H/N-H annulation leading to the intermediate 2-pyridone with an exocyclic secondary amide, and subsequently undergo the unexpected stereoselective C-H alkenylation to realize fully substituted 2-pyridones bearing an exocyclic anti alkenyl group. On the addition of K2CO3, however, the transformation of fumaramides with 1,2-dialkyl ethyne undergoes two conventional C-H/N-H annulations to provide 2,6-naphthyridine-1,5-diones in high yield. The two procedures can be successfully enlarged to gram-scales without erosion of the yields. In addition, some 2-pyridones and 2,6-naphthyridine-1,5-diones emitting clear ultraviolent and fluorescent light, indicating the potential utility of this work in organic light-emitting materials.