1: 90 percent / trifluoroacetic acid / 1 h / Ambient temperature 2: 41 percent / thiourea / acetonitrile; ethanol / 72 h / 40 °C 3: 14 percent / triphenylphosphine, 2,2'dithiopyridine / acetonitrile / 6 h / Heating 4: 100 percent / H2 / 10 percent Pd/C / ethanol / 16 h View Scheme