1: 95 percent / 520 °C / 0.1 Torr 2: 1.) isoamyl nitrite, trichloroacetic acid / 1.) THF, RT, 2 h, 2.) 1,2-dichloroethane, reflux, 30 min 3: 85 percent / diiron enneacarbonyl / benzene / 40 h / Heating View Scheme

1: dimethyl acetylenedicarboxylate / flash vacuum pyrolysis: 600 deg C, 0.03 mmHg, 30-120 deg C, 3 h 2: 90 percent / H2 / 10percent Pd/C / ethanol / 1 h / 1137.7 Torr 3: 65 percent / polyphosphoric acid / 4 h / 170 °C View Scheme