1: 84 percent / crown-18 ether / acetonitrile / 4 h / 25 °C 2: 45 percent / hydrazine / ethanol / 72 h / 25 °C 3: 56 percent / N-methyl morpholine / methanol / 4 h / Heating 4: 83.5 percent / 1 N HCl / trifluoroacetic acid / 55 °C 5: 42 percent / sodium dithionite / dimethylformamide / 0.25 h / 50 °C 6: dimethylformamide / 2 h / 100 - 120 °C View Scheme

1: 84 percent / crown-18 ether / acetonitrile / 4 h / 25 °C 2: 45 percent / hydrazine / ethanol / 72 h / 25 °C 3: 56 percent / N-methyl morpholine / methanol / 4 h / Heating 4: 83.5 percent / 1 N HCl / trifluoroacetic acid / 55 °C 5: 42 percent / sodium dithionite / dimethylformamide / 0.25 h / 50 °C 6: dimethylformamide / 2 h / 100 - 120 °C 7: 33 percent / 1 N NaOH / H2O / 0.5 h / 80 °C 8: thionyl chloride / benzene / 2 h / Heating 9: 2.) HCl / 1.) ether, methylene chloride, RT, 1 h View Scheme