1: lithium diisopropylamide / tetrahydrofuran / 0.83 h / -70 °C 2: 1.5 M tetrafluoroboric acid, H2O / tetrahydrofuran / 2 h / Ambient temperature 3: 95 percent / trifluoroacetic anhydride, trifluoroacetic acid / 16 h / Ambient temperature View Scheme

tetrafluoroboric acid; lithium diisopropyl amide 1.) THF, -78 deg C, 45 min, 2.) RT, 16 h; Yield given. Multistep reaction;