Asymmetric Synthesis of Allylic Fluorides via Fluorination of Racemic Allylic Trichloroacetimidates Catalyzed by a Chiral Diene-Iridium Complex

The ability to use racemic allylic trichloroacetimidates as competent electrophiles in a chiral bicyclo[3.3.0]octadiene-ligated iridium-catalyzed asymmetric fluorination with Et3N·3HF is described. The methodology represents an effective route to prepare a wide variety of α-linear, α-branching, and β-heteroatom substituted allylic fluorides in good yields, excellent branched-to-linear ratios, and high levels of enantioselectivity. Additionally, the catalytic system is amendable to the fluorination of optically active allylic trichloroacetimidate substrates to afford the fluorinated products in good yields with exclusively branched selectivity. Excellent levels of catalyst-controlled diastereoselectivities using either (R,R) or (S,S)-bicyclo[3.3.0]octadiene ligand are observed. The synthetic utility of the fluorination process is illustrated in the asymmetric synthesis of 15-fluorinated prostaglandin and neuroprotective agent P7C3-A20.