Palladium-Catalyzed Cascade Reaction of Indoles with α,α-Difluoro-β,γ-Unsaturated Ketones: One-Step Access to 2-Fluorocarbazoles.

A practical synthesis of pharmacologically and materially relevant fluorinated carbazoles is highly desirable yet remains challenging. Herein, we report an efficient route to 2-fluorocarbazoles via a Pd(0)/Cu(I)-cocatalyzed tandem reaction between readily available α,α-difluoro-β,γ-unsaturated ketones and indoles. This protocol involves sequential Pd(0)-catalyzed defluorination and indole addition, followed by Cu(I)-promoted benzannulation. A variety of 2-fluorocarbazoles were obtained in good to excellent yields, and the synthetic utility was demonstrated by a gram-scale reaction. This method provides a practical and modular route to this valuable class of fluorinated heterocycles.