1: 20 percent / ethylaluminum dichloride / CH2Cl2; toluene / Ambient temperature 2: 36 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 0.5 h / Ambient temperature View Scheme

1: 41 percent / EtAlCl3 / CH2Cl2; toluene / 0.67 h / Ambient temperature 2: 95 percent / p-toluenesulfonic acid monohydrate, Bio-Rex 9 / methanol; H2O / 7 h / Ambient temperature View Scheme

1: trimethylsilyl triflate / 1,2-dichloro-ethane / 0.5 h 2: 89 percent / H2S, NaSH / methanol / 1 h / Heating 3: 65 percent / tetra-n-butylammonium fluoride (TBAF) / tetrahydrofuran / 24 h / Ambient temperature View Scheme