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Parrain, J.-L.; Thibonnet, J., Science of Synthesis, (2005) 26, 772.
1-Fluoro-4-hydroxy-1,4-diazabicyclo[2.2.2]octane bis(tetrafluoroborate) (Accufluor, NFTh) acting as a fluorine atom transfer reagent and with methanol as solvent enables direct regiospecific fluoro functionalization of the α-carbonyl position in ketones without prior activation of the target molecules.[156] A practical enantioselective fluorination reaction applicable to both cyclic and acyclic carbonyl compounds using commercially or readily available cinchona alkaloid derivatives and 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) has been proposed. Applied to α-alkoxy ketone 68, this method yields α-fluoro ketone 69 in 80% ee (Scheme 32).[157]
Meeeee 88 Meeeeeeeeeee ee α-Meeeee Meeeeee[888]
Meeeeeeeeeee Meeeeeeee
Meeee 8-Meeeee-8-eee-8,8-eeeeeee-8-eeeeeeeeee-8-eeeeeeeeeee (88); Meeeeee Meeeeeeee:[888]
M eeee ee eeeee 8-eee-8,8-eeeeeee-8-eeeeeeeeee-8-eeeeeeeeeee (88; 88 ee, 8.888 eeee) ee MM8Me8 eee eeeee ee MM-MMMM-MM8 [eeeeeeee ee eeee eeee MMMM (888 ee, 8.888 eeee) eee Meeeeeeeeee (88%; 88 ee, 8.888 eeee) ee MeMM (8 eM) ee eee eeeeeeee ee 8-Å eeeeeeeee eeeeee ee ee eee 8 e] ee −88°M eeeee e M8 eeeeeeeeee. Meeee eeeeeeee eee 8 e, M8M eee eeeee eee eee eeeeeee eee eeeeeeeee eeee MeMMe. Mee eeeeeee eeeee eee eeeeee eeee 8% ee MMe, eee. ee MeMMM8, eeeee, eee eeeee (Me8MM8). Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee ee eeee e eeeee eee, eeeee eee eeeeeeee ee eeeeeeeeeee MMM (eeeeee eee, MeMMe/eeeeee 8:8) ee eeee eee eeeeeee ee e eeeeeeeee eee; eeeee: 88.8 ee (88%, 88% ee) (eeeeeeeeee ee MMMM; Meeeeeeee MM, eMeMM/eeeeee 8:8).
References
[156] | Meeeeee, M.; Meeee, M.; Meeee, M., Meeeeeeee, (8888), 8888. |
[157] | Meeeeee, M.; Meeeee, M.; Meeeeeee, M., M. Me. Meee. Mee., (8888) 888, 88888. |