sodium hydroxide; sodium tetrahydroborate; mercury(II) diacetate in tetrahydrofuran T=4°C; 1.5 h;

Multi-step reaction with 5 steps 1: 70 percent / Hg(OAc)2, NaOH, NaBH4 / tetrahydrofuran / 1.5 h / 4 °C2: 45 percent / Jone's reagent3: 75 percent / KH, Et3B / tetrahydrofuran / 0 - 25 °C4: 74 percent / KO-t-Bu / 1,2-dimethoxy-ethane / 45 °C5: 75 percent / DIBAL / benzene / 5 h / 25 °C