1: 83 percent / toluene-p-sulphonic acid / benzene / 48 h / Heating 2: 1.) sodium periodate, 2.) CaCO3 / 1.) water, methanol, r.t., 24 h, 2.) toluene, reflux, 16 h 3: 90 percent / tetramethylguanidine / 72 h / Ambient temperature 4: 1.) sodium methoxide, 2.) ammonium acetate, TiCl3 / 1.) methanol, 20 min, 2.) water, 1.5 h, r.t. 5: 79 percent / trifluoroacetic acid; H2O / 6 h / Ambient temperature View Scheme