1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h 2: 53 percent / tetrahydrofuran / 0.5 h / 0 °C 3: 1) 95percent aq. H2SO4, 2) CF3SO3H / 1) room temp., 40 min; 2) 1 h at room temp., then 2.5 h at 45-55 deg C, then 2.66 h at 60-70 deg C 4: 98 percent / Et3N / toluene / 0.42 h / 80 °C 5: 67 percent / 13percent aq. KOH / ethanol / 25 h / Heating 6: 89 percent / NaBH4 / methanol / 1.8 h / 0 °C View Scheme

1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h 2: 61 percent / tetrahydrofuran / 1 h / 0 °C 3: 1) 87percent aq. H2SO4; 2) CF3SO3H / 1) room temp., 30 min; 2) 115 deg C, 1 h 4: 84 percent / Et3N / toluene / 0.5 h / 80 °C 5: 67 percent / 13percent aq. KOH / ethanol / 42 h / Heating 6: 85 percent / NaBH4 / methanol / 0.5 h / 0 °C View Scheme

Multi-step reaction with 2 steps 1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h2: 53 percent / tetrahydrofuran / 0.5 h / 0 °C  

Multi-step reaction with 4 steps 1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h2: 53 percent / tetrahydrofuran / 0.5 h / 0 °C3: 1) 95percent aq. H2SO4, 2) CF3SO3H / 1) room temp., 40 min; 2) 1 h at room temp., then 2.5 h at 45-55 deg C, then 2.66 h at 60-70 deg C4: 98 percent / Et3N / toluene / 0.42 h / 80 °C  

Multi-step reaction with 5 steps 1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h2: 53 percent / tetrahydrofuran / 0.5 h / 0 °C3: 1) 95percent aq. H2SO4, 2) CF3SO3H / 1) room temp., 40 min; 2) 1 h at room temp., then 2.5 h at 45-55 deg C, then 2.66 h at 60-70 deg C4: 98 percent / Et3N / toluene / 0.42 h / 80 °C5: 67 percent / 13percent aq. KOH / ethanol / 25 h / Heating  

With  bromine; silver nitrate in  methanol Show Experimental Procedure  

Multi-step reaction with 4 steps 1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h2: 61 percent / tetrahydrofuran / 1 h / 0 °C3: 1) 87percent aq. H2SO4; 2) CF3SO3H / 1) room temp., 30 min; 2) 115 deg C, 1 h4: 84 percent / Et3N / toluene / 0.5 h / 80 °C  

Multi-step reaction with 3 steps 1: 1) AgNO3, Br2; 2) DBU / 1) room temp., 8.5 h; 2) CH2Cl2, reflux, 2.33 h2: 53 percent / tetrahydrofuran / 0.5 h / 0 °C3: 88percent aq. H2SO4 / methanol / 0.58 h / Ambient temperature