Hydrogen-Bonding Phase-Transfer Catalyst Enabled Asymmetric Fluorination

Key words

phase-transfer catalysis - nucleophilic fluorination - hydrogen bonding - bis-urea catalysis

Significance

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.

Comment

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.