1: 61 percent / tetrahydrofuran / 1 h / 0 °C 2: 1) 87percent aq. H2SO4; 2) CF3SO3H / 1) room temp., 30 min; 2) 115 deg C, 1 h 3: 84 percent / Et3N / toluene / 0.5 h / 80 °C 4: 67 percent / 13percent aq. KOH / ethanol / 42 h / Heating 5: 85 percent / NaBH4 / methanol / 0.5 h / 0 °C View Scheme

With  bromine; silver nitrate in  methanol Show Experimental Procedure  

Multi-step reaction with 3 steps 1: 61 percent / tetrahydrofuran / 1 h / 0 °C2: 1) 87percent aq. H2SO4; 2) CF3SO3H / 1) room temp., 30 min; 2) 115 deg C, 1 h3: 84 percent / Et3N / toluene / 0.5 h / 80 °C