1: ethyl chloroformate, triethylamine / CHCl3 / 3.5 h / Ambient temperature 2: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 3: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 4: 0.350 g / PPE / 1.5 h / 80 °C 5: 84 percent / dimethylformamide / Ambient temperature 6: 88 percent / KOH / 2-methyl-propan-2-ol; H2O / 1 h / 50 - 60 °C View Scheme

1: ethyl chloroformate, triethylamine / CHCl3 / 3.5 h / Ambient temperature 2: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 3: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 4: 0.350 g / PPE / 1.5 h / 80 °C View Scheme

1: ethyl chloroformate, triethylamine / CHCl3 / 3.5 h / Ambient temperature 2: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 3: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 4: 0.350 g / PPE / 1.5 h / 80 °C 5: 84 percent / dimethylformamide / Ambient temperature 6: 88 percent / KOH / 2-methyl-propan-2-ol; H2O / 1 h / 50 - 60 °C 7: 62 percent / KHCO3 / dimethylformamide / 5 h / Ambient temperature View Scheme

chloroformic acid ethyl ester; triethylamine in chloroform 3.5 h; Ambient temperature; Yield given;

1: ethyl chloroformate, triethylamine / CHCl3 / 3.5 h / Ambient temperature 2: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 3: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 4: 0.350 g / PPE / 1.5 h / 80 °C 5: 84 percent / dimethylformamide / Ambient temperature View Scheme

1: triethylamine, ethyl chloroformate / CHCl3 / 3.5 h / Ambient temperature 2: 1.) sodium hydride / 1.) THF, RT, 1 h, 2.) THF, RT, 1 h 3: 67 percent / dimethylformamide / 2 h / Ambient temperature 4: diphenyl ether / 0.2 h / 250 °C 5: 90 percent / trifluoromethanesulfonic acid, trifluoroacetic acid, anisole / 2 h / Ambient temperature 6: 1.) sodium / 1.) ethanol, 0 deg C, 1,5 h, 2.) ethanol, RT, 3,5 h 7: 89 percent / conc. sulfuric acid / 1 h / 0 °C 8: sodium hydroxide, water / ethanol / 2 h / Heating 9: 73 percent / pyridine / 2 h / 100 °C View Scheme

1: triethylamine, ethyl chloroformate / CHCl3 / 3.5 h / Ambient temperature 2: 1.) sodium hydride / 1.) THF, RT, 1 h, 2.) THF, RT, 1 h 3: 67 percent / dimethylformamide / 2 h / Ambient temperature 4: diphenyl ether / 0.2 h / 250 °C 5: 90 percent / trifluoromethanesulfonic acid, trifluoroacetic acid, anisole / 2 h / Ambient temperature 6: 1.) sodium / 1.) ethanol, 0 deg C, 1,5 h, 2.) ethanol, RT, 3,5 h 7: 89 percent / conc. sulfuric acid / 1 h / 0 °C 8: sodium hydroxide, water / ethanol / 2 h / Heating 9: 73 percent / pyridine / 2 h / 100 °C View Scheme