Effect of BF3 on the enantioselective reduction of trifluoromethyl ketones using a chiral lactam alcohol with borane

The addition of BF3·THF to an oxazaborolidine catalyst prepared in situ from chiral lactam alcohol 2 and borane enhanced the enantioselectivities (up to 90% ee) and yield (up to 91%) during the reduction of reactive trifluoromethyl ketones at room temperature.

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(S)-2,2,2-Trifluoro-1-biphenylethanolC14H11F3O[α]D25 = +22.7 (c 0.08, CHCl3), 90% eeSource of chirality: Asymmetric synthesisAbsolute configuration: (S)

(S)-2,2,2-Trifluoro-1-(4-bromo-4′-biphenyl)ethanolC14H10BrF3O[α]D25 = +12.3 (c 0.08, CHCl3), 71% eeSource of chirality: Asymmetric synthesisAbsolute configulation: (S)