1: 99 percent / p-TsOH / tetrahydrofuran; H2O; propan-2-ol / 1 h / Heating 2: 1) sodium hexamethyldisilazide / 1) THF, toluene, 2 h, 25 deg C, 2) THF, a) -100 deg C, 30 min, b) to 25 deg C, 3 h 3: p-TsOH / tetrahydrofuran; H2O / 0.08 h / Heating 4: tetrahydrofuran; hexamethylphosphoric acid triamide; toluene / -100 to 0 deg C, 3-4 h 5: 90 percent / Li, NH3, t-BuOH / tetrahydrofuran / 0.25 h / -40 °C View Scheme

1: 99 percent / p-TsOH / tetrahydrofuran; H2O; propan-2-ol / 1 h / Heating 2: 1) sodium hexamethyldisilazide / 1) THF, toluene, 2 h, 25 deg C, 2) THF, a) -100 deg C, 30 min, b) to 25 deg C, 3 h 3: p-TsOH / tetrahydrofuran; H2O / 0.08 h / Heating 4: tetrahydrofuran; hexamethylphosphoric acid triamide; toluene / -100 to 0 deg C, 3-4 h 5: 90 percent / Li, NH3, t-BuOH / tetrahydrofuran / 0.25 h / -40 °C 6: 70 percent / Ph3P, diethyl azodicarboxylate / toluene / 0.5 h View Scheme