Rhodium(III)-Catalyzed C-H Alkynylation of Ferrocenes with Hypervalent Iodine Reagents.

Rapid access to mono- or dialkynylation of ferrocene with ethynylbenziodoxolones as the alkynylation reagents was achieved via rhodium-catalyzed direct C-H bond functionalization at room temperature. Mono- and dialkynylation were easily modulated by varying the sterical volume of the directing group, such as pyridine and isoquinoline, and amount of hypervalent iodine reagents. A wide range of ferrocene-based alkynylation products could be obtained in up to 94% yield, and a gram-scale reaction also proceeded smoothly with high efficiency.