sodium tetrahydroborate in methanol T=0°C; 1.5 h;

1: 55 percent / p-toluenesulfonic acid / toluene / 5 h / Heating 2: 45 percent / potassium tert-butoxide / 1.) 0.25 h, 2.) heating, 4 h 3: 86 percent / aq. hydrochloric acid / 1,2-dimethoxy-ethane; H2O / 24 h / Ambient temperature 4: 53 percent / sodium borohydride / methanol / 1.5 h / 0 °C View Scheme

1: 45 percent / potassium tert-butoxide / 1.) 0.25 h, 2.) heating, 4 h 2: 86 percent / aq. hydrochloric acid / 1,2-dimethoxy-ethane; H2O / 24 h / Ambient temperature 3: 53 percent / sodium borohydride / methanol / 1.5 h / 0 °C View Scheme

1: 86 percent / aq. hydrochloric acid / 1,2-dimethoxy-ethane; H2O / 24 h / Ambient temperature 2: 53 percent / sodium borohydride / methanol / 1.5 h / 0 °C View Scheme