Rhodium-Catalyzed Double Alkynylation of Isatins

Abstract We report a rhodium-catalyzed strategy utilizing alkynylating reagents to access functionalized 3-hydroxy-2-oxindoles, a privileged structural motif. Mechanistic studies and density functional theory (DFT) analysis support a proposed mechanism wherein the products arise from initial 1,2-addition of a rhodium acetylide to the carbonyl of the isatin starting material. The high reactivity of the alkyne-containing intermediates prime them for a subsequent 1,2-migratory insertion of the rhodium acetylide, affording the enyne-containing products.