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Hydrogen-Bonding Phase-Transfer Catalyst Enabled Asymmetric Fluorination
Asymmetric Nucleophilic Fluorination under Hydrogen Bonding Phase-Transfer Catalysis.
18 July 2018 (online)
Key wordsphase-transfer catalysis - nucleophilic fluorination - hydrogen bonding - bis-urea catalysis
Gouverneur and co-workers merge two fundamental strategies of modern catalyst design, hydrogen-bonding interactions and phase-transfer catalysis, to report a chiral bis-urea catalyzed asymmetric nucleophilic fluorination of episulfonium salts formed in situ. The fluorinated products are formed in good to excellent yields and moderate to good enantioselectivities by using CsF.
Hydrogen-bonding phase-transfer catalysis (HB PTC) has been previously reported in highly enantioselective nitro-Mannich reactions (B. Wang, Y. Liu, C. Sun, Z. Wei, J. Cao, D. Liang, Y. Lin, H. Duan Org. Lett. 2014, 16, 6432). Gouverneur and co-workers develop such catalysts to solve a synthetic challenge; namely, to enable an asymmetric fluorination reaction using a safe and readily accessible inorganic fluorine source. Henceforth, the expansion of HB PTC to other systems is expected.