1: 88 percent / aq. trifluoroacetic acid / 1 h / 20 °C 2: 84 percent / Bu4NBr; (Bu3Sn)2O / toluene / 2 h / Heating 3: 93 percent / PPh3; diisopropyl azodicarboxylate / toluene / 48 h / 20 °C 4: 97 percent / H2 / Pd/C / methanol; ethyl acetate / 20 °C View Scheme

1: 88 percent / aq. trifluoroacetic acid / 1 h / 20 °C 2: 84 percent / Bu4NBr; (Bu3Sn)2O / toluene / 2 h / Heating 3: 93 percent / PPh3; diisopropyl azodicarboxylate / toluene / 48 h / 20 °C 4: 97 percent / H2 / Pd/C / methanol; ethyl acetate / 20 °C View Scheme

1: toluene-p-sulphonic acid / acetone; H2O / 0.83 h / 20 °C 2: 1) tetrabutylammonium bromide, dibutyltin oxide 3: 1.2 g / pyridine / 12 h / 20 °C 4: sodium hydroxide / methanol / 0.25 h / Heating 5: M HCl / methanol / 0.67 h / Heating View Scheme

With  acetic acid T=100°C;