1: p-TsOH / tetrahydrofuran; H2O / 0.08 h / Heating 2: tetrahydrofuran; hexamethylphosphoric acid triamide; toluene / -100 to 0 deg C, 3-4 h 3: 90 percent / Li, NH3, t-BuOH / tetrahydrofuran / 0.25 h / -40 °C View Scheme

1: p-TsOH / tetrahydrofuran; H2O / 0.08 h / Heating 2: tetrahydrofuran; hexamethylphosphoric acid triamide; toluene / -100 to 0 deg C, 3-4 h 3: 90 percent / Li, NH3, t-BuOH / tetrahydrofuran / 0.25 h / -40 °C 4: 70 percent / Ph3P, diethyl azodicarboxylate / toluene / 0.5 h View Scheme