sodium tetrahydroborate in trifluoroacetic acid 1 h;

Fremy’s salt 1.) pH 7 buffer, Me2CO, 10 min, 2.) room temperature, overnight; Yield given. Multistep reaction;

1: 1.) potassium nitrosodisulfonate / 1.) pH 7 buffer, Me2CO, 10 min, 2.) room temperature, overnight 2: 66 percent / boron trifluoride etherate / tetrahydrofuran; CH2Cl2 / 28 h / Ambient temperature 3: 85 percent / KOH / methanol; H2O / 5 h / Heating View Scheme