1: 1) N-bromosuccinimide, 2) K2CO3 / 1) MeOH, 23 deg C, 2 h, 2) THF, H2O, 23 deg C, 2 h 2: 90 percent / NaBH4 / ethanol / 2 h / Heating 3: 80 percent / H2O2, pyridine / CH2Cl2; tetrahydrofuran / 6 h / 23 °C 4: 87 percent / NEt3, 4-dimethylaminopyridine / 12 h / 60 °C View Scheme

tetrabutyl ammonium fluoride in tetrahydrofuran 1 h; Ambient temperature;