Dowex 50W-X4 acidic ion-exchange resin in 1,2-dichloro-ethane T=90°C; Pictet-Spengler cyclisation; Automated synthesizer;

trifluoroacetic acid in acetonitrile T=0°C; 2 h;

acetic acid in acetonitrile 3.5 h; Heating;

trifluoroacetic acid in acetonitrile 0.5 h; Ambient temperature;

acetic acid in acetonitrile 5 h; Heating;

formaldehyd; sulfuric acid Erhitzen des Reaktionsprodukts mit wss. H2SO4;

1: 83 percent / tetrahydrofuran / 12 h / 20 °C 2: 83 percent / 1,4-bis(methylamino)pyridine, DCC / CH2Cl2 / 18 h / 20 °C 3: 79 percent / NaH / tetrahydrofuran / 4 h / 20 °C 4: 79 percent / LiBr, H2O / dimethylformamide / 12 h / Heating 5: p-TsOH / toluene / 12 h / Heating 6: 1.) hydroquinone, 2.) 20percent AcOH / 1.) THF, 60 deg C, 2 d,2.) H2O, THF, 40 deg C, 72 h 7: 76 percent / LiOH, 30percent H2O2 / methanol / 5 h / 20 °C 8: 1.) NH2NH2*H2O, 2.) KOH, 3.) conc. HCl / 1.) diethylene glycol, 160 deg C, 1 h, 2.) 220-225 deg C, 4 h, 3.) H2O, 0 deg C, 4.) Et2O, 0 deg C 9: 1.) POCl3, 2.) 1M LiClO4, 3.) H2, 4.) 30percent ammonia / 3.) 10percent Pd/C / 1.) CH3CN, 100 deg C, 4 h, 2.) CH2Cl2, 10 min, 3.) DMF, 1 bar, 5 h 10: 70 percent / sodium bis(trimethylsilyl)amide / toluene; tetrahydrofuran / 2 h / 20 °C 11: 65 percent / tert-butyl nitrite, sodium bis(trimethylsilyl)amide / toluene; tetrahydrofuran / 1.5 h / 50 °C 12: p-TsOH, paraformaldehyde / acetic acid / 5 h / 100 - 105 °C 13: 40 percent / t-BuOK / 2 h / 20 °C View Scheme

benzotriazol-1-ol; N'-(3-dimethylaminopropyl)-N-ethylcarbodiimide in dichloromethane T=25°C;

potassium phosphate; [Rh(trop2NH)(PPh3)]+(CF3SO2)-; methacrylic acid methyl ester in tetrahydrofuran T=0°C;

in pyridine T=20°C;