1: 90 percent / piperidine, pyridine / 0.17 h / 100 °C 2: 100 percent / H2 / PtO2 / methanol / 3 h 3: 86 percent / polyphosphonic acid / 0.17 h / 80 - 90 °C 4: 96 percent / H2, sodium acetate / 5percent Pd/C / acetic acid / 2 h View Scheme