1: TBAF / tetrahydrofuran / 4 h / 75 °C 2: 81 percent / ZnBr2 / CH2Cl2; methanol / 0.33 h View Scheme

1: TBAF / tetrahydrofuran / 4 h / 75 °C 2: 81 percent / ZnBr2 / CH2Cl2; methanol / 0.33 h 3: 80 percent / pyridine / 20 h / Ambient temperature 4: 69 percent / o-chlorophenylphosphorodichloridate / pyridine / 48 h / Ambient temperature 5: 75 percent / NH4OH / dioxane / 2.5 h / Ambient temperature 6: 82 percent / NaOEt / 24 h / Ambient temperature 7: 77 percent / methanol / 4 h / Heating View Scheme

1: TBAF / tetrahydrofuran / 4 h / 75 °C 2: 81 percent / ZnBr2 / CH2Cl2; methanol / 0.33 h 3: 80 percent / pyridine / 20 h / Ambient temperature 4: 69 percent / o-chlorophenylphosphorodichloridate / pyridine / 48 h / Ambient temperature 5: 75 percent / NH4OH / dioxane / 2.5 h / Ambient temperature 6: 82 percent / NaOEt / 24 h / Ambient temperature View Scheme

1: TBAF / tetrahydrofuran / 4 h / 75 °C 2: 81 percent / ZnBr2 / CH2Cl2; methanol / 0.33 h 3: 80 percent / pyridine / 20 h / Ambient temperature 4: 69 percent / o-chlorophenylphosphorodichloridate / pyridine / 48 h / Ambient temperature 5: 75 percent / NH4OH / dioxane / 2.5 h / Ambient temperature 6: 82 percent / NaOEt / 24 h / Ambient temperature 7: 77 percent / methanol / 4 h / Heating 8: 78 percent / pyridine / 2 h View Scheme

With  2,2'-azo-bisisobutyronitrile; tri-n-butyl-tin hydride in  toluene T=110 - 120°C; 3 h;   

Multi-step reaction with 2 steps 1: 71 percent / DMAP / acetonitrile / 20 h / Ambient temperature2: AIBN, Bu3SnH / toluene / 3 h / 85 °C