NaBH(HFIP)3 in tetrahydrofuran; hexafluoroisopropyl alcohol T=0°C; 2 h; chemoselective reaction;

1.1: magnesium / diethyl ether / 2.5 h / 20 °C 1.2: 3 h / -78 - 0 °C 2.1: phosphorus tribromide / dichloromethane / 1 h / 0 °C 3.1: diMe-Imd-BH3; t-DDT; t-BuON=NOt-Bu / benzene / 2 h / 80 °C View Scheme

1: 1) sodium hexamethyldisilazide / 1) THF, toluene, 25 deg C, 2 h, 2) THF, a) -100 deg C, 30 min, b) to 25 deg C, 3 h 2: p-TsOH / tetrahydrofuran; H2O / 0.08 h / Heating 3: 1) sodium hexamethyldisilazide / 1) THF, toluene, 1 h,k 20 deg C, 2) -100 to 0 deg C, 4 h 4: 90 percent / Li, NH3, t-BuOH / tetrahydrofuran / -40 °C 5: p-TsOH / tetrahydrofuran; H2O / 0.17 h / Heating 6: 1-methylcyclohex-1-ene, NaClO2, H2NSO3H / CH2Cl2; H2O / 1) 0 deg C, 15 min, 2) to 25 deg C, 30 min 7: 68 percent / Ph3P, diethyl azodicarboxylate / tetrahydrofuran / 1 h View Scheme