1.1: 4-(N,N-dimethlyamino)pyridine; triethylamine / dichloromethane / 0 - 5 °C 2.1: toluene-4-sulfonic acid / dichloromethane / 25 - 30 °C 3.1: water; sodium hydroxide / tetrahydrofuran; methanol / 2 h / 25 - 30 °C 4.1: hydrogenchloride / water / 25 - 30 °C / pH 6.5 - 7 5.1: N-ethyl-N,N-diisopropylamine / dichloromethane / 25 - 30 °C 5.2: 1.5 h / 0 - 5 °C 6.1: n-butyllithium / tetrahydrofuran; hexane / -15 - 0 °C / Inert atmosphere 6.2: 19 h / -5 - 2 °C / Inert atmosphere 7.1: ethyl acetate / 15 h / 25 - 30 °C / Inert atmosphere 8.1: sulfuric acid; water / 2 h / 0 - 10 °C / Inert atmosphere 9.1: ethyl acetate / 18 h / 25 - 30 °C / Inert atmosphere 10.1: acetic acid / dichloromethane; water / 0.5 h / pH 3.5 - 4 10.2: 0.5 h / 25 - 30 °C View Scheme