Structure Dependence in Asymmetric Deprotonative Fluorination and Fluorocyclization Reactions of Allylamine Derivatives with Linked Binaphthyl Dicarboxylate Phase-Transfer Catalyst
Tomoki Niwa, Kousuke Nishibashi, Hitomi Sato, Kiyoshi Ujiie, Kenji Yamashita, Hiromichi Egami and Yoshitaka Hamashima*
*School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan, Email: hamashimau-shizuoka-ken.ac.jp
T. Niwa, K. Nishibashi, H. Sato, K. Ujiie, K. Yamashita, H. Egami, Y. Hamashima, J. Am. Chem. Soc., 2021, 143, 16599-16609.
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A dianionic phase-transfer catalyst enables an asymmetric fluorofunctionalization of γ,γ-disubstituted allylamine derivatives. Depending on the substituents on the alkene moiety, the reaction afforded chiral allylic fluorides and fluorinated dihydrooxazines in a highly enantioselective manner.
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General experimental procedure for the asymmetric deprotonative fluorination of allylic amides
To a solution of allylamine derivative (24.3 mg, 0.1 mmol), phase-transfer catalyst (9.7 mg, 10 mol %), K3PO4 (31.8 mg, 1.5 equiv) and Na2SO4 (50 mg) in toluene (1 mL) was added Selectfluor (53.1 mg, 1.5 equiv) at 25 °C. The reaction mixture was stirred for 24 h at the same temperature, then the reaction mixture was filtrated through a pad of Celite. The filtrate was evaporated under reduced pressure. The resulting residue was purified by column chromatography on silica gel (n-hexane / ethyl acetate = 5/1) to provide the product as a colorless oil (20.5 mg, 79%). The ee was determined by chiral HPLC analysis.
1,2-fluoroamines, allylic fluorides, Selectfluor, organocatalysis