Reaction Steps
A solution containing 30 (1.09 g, 1.27 mmol) in DCM (20 mL) was cooled to 0° C. TFA (4 mL) was added via pipette and the reaction was monitored until TLC analysis revealed complete consumption of 30 (˜2 h). TLC analysis, 10% MeOH/DCM, Rf(30)=0.5; Rf(31)=0.4. The solvent was removed on a rotary evaporator and the residue was dissolved in EtOAc. The EtOAc solution was washed twice with saturated aqueous NaHCO3 and once with brine. The combined aqueous washes were back-extracted with EtOAc and the organic extracts were dried over anhydrous Na2SO4, filtered, and concentrated to afford 0.83 g (quant.) of 31 as a yellow solid which was used without further purification. 1H NMR (CDCl3, 300 MHz) δ8.09 (dd, J=5.1, 8.7 Hz, 1H), 6.97 (m, 2H), 4.52 (m, 1H), 4.50 (d, J=8.7 Hz, 1H), 4.11 (m, 1H), 3.71 (br d, J=11.1 Hz, 1H), 3.51-3.32 (m, 2H), 2.74 (app t, J=12.6 Hz, 1H), 2.30 (br s, 4H), 1.92 (m, 1H), 1.68 (m, 2H), 1.41 (m, 1H), 1.03 (m, 6H) ppm. 13C NMR (CDCl3, 75 MHz) δ174.3, 171.4, 160.6 (d, JC-F=232.5 Hz), 136.8 (d, JC-F=7.5 Hz), 127.4 (d, JC-F=3.7 Hz), 125.0, 122.4 (d, JC-F=7.5 Hz), 109.6, 108.7 (d, JC-F=22.5 Hz), 95.2 (d, JC-F=22.5 Hz), 58.0, 47.3, 41.9, 30.0, 28.5, 28.5, 24.1, 19.9, 17.6 ppm.
