1: 72 percent / sodium hydroxide / methanol / 4 h / Heating 2: 89 percent / ethyl acetate / 5 h / 50 °C 4: 54 percent / triphenylphosphine / dimethylformamide / 86 h / Heating View Scheme

1: 72 percent / sodium hydroxide / methanol / 4 h / Heating 2: 89 percent / ethyl acetate / 5 h / 50 °C 4: 54 percent / triphenylphosphine / dimethylformamide / 86 h / Heating 5: 54 percent / tetrahydrofuran / 1.) r.t., 30 min; 2.) reflux, 1 h View Scheme