Ruthenium-Catalyzed Oxidative Annulation and Hydroarylation of Chromene-3-carboxamides with Alkynes via Double C-H Functionalization

Article abstract of DOI:10.1021/acs.joc.7b00008

Ruthenium-catalyzed oxidative annulation of 2H-chromene-3-carboxamides with alkynes has been achieved by using the directing group nature of amide in the presence of Cu(OAc)₂·H₂O as an oxidant and AgNTf₂ as an additive. This reaction offers a broad substrate scope, and both symmetrical and unsymmetrical alkynes can be harnessed. High regioselectivity was achieved in the case of unsymmetrical alkynes. In addition, we have also accomplished double C-H activation by employing an excess of alkyne, where both annulation and hydroarylation took place regio- and stereoselectively in one pot, with the catalyst playing a dual role. While the first C-H functionalization could involve Ru-N covalent bond, the second C-H functionalization most likely involves Ru-O coordinate bond. The structures of key products are confirmed by X-ray crystallography.