1.1: chloroformic acid ethyl ester; triethylamine / dichloromethane / 2 h / 0 °C / |Inert atmosphere 1.2: 2.5 h / 0 - 25 °C / |Inert atmosphere 2.1: cesium fluoride; methanol / 3 h / 25 °C / |Inert atmosphere View Scheme

methanol; cesium fluoride T=25°C; 3 h; Inert atmosphere; Overall yield = 0.98 g;

1.1: 2,3-dicyano-5,6-dichloro-p-benzoquinone / dichloromethane; water / 0.17 h / 0 °C 2.1: chloroformic acid ethyl ester; triethylamine / dichloromethane / 2 h / 0 °C 2.2: 2.5 h / 0 - 20 °C 3.1: cesium fluoride; methanol / 3 h / 20 °C View Scheme

1.1: trifluoroacetic acid / 48 h / 25 °C 2.1: 2,2,6,6-tetramethylpiperidinyl-lithium / tetrahydrofuran / 0.5 h / -78 °C 2.2: 6.5 h / -78 - 0 °C 3.1: (-)-Ipc2BH / tetrahydrofuran / 2 h / 0 °C 3.2: 1 h / 0 - 20 °C 4.1: lithium hydroxide hydrate / methanol / 24 h / 45 °C 4.2: pH 4 5.1: 2,3-dicyano-5,6-dichloro-p-benzoquinone / dichloromethane; water / 0.17 h / 0 °C 6.1: chloroformic acid ethyl ester; triethylamine / dichloromethane / 2 h / 0 °C 6.2: 2.5 h / 0 - 20 °C 7.1: cesium fluoride; methanol / 3 h / 20 °C View Scheme

1.1: 2,2,6,6-tetramethylpiperidinyl-lithium / tetrahydrofuran / 0.5 h / -78 °C 1.2: 6.5 h / -78 - 0 °C 2.1: (-)-Ipc2BH / tetrahydrofuran / 2 h / 0 °C 2.2: 1 h / 0 - 20 °C 3.1: lithium hydroxide hydrate / methanol / 24 h / 45 °C 3.2: pH 4 4.1: 2,3-dicyano-5,6-dichloro-p-benzoquinone / dichloromethane; water / 0.17 h / 0 °C 5.1: chloroformic acid ethyl ester; triethylamine / dichloromethane / 2 h / 0 °C 5.2: 2.5 h / 0 - 20 °C 6.1: cesium fluoride; methanol / 3 h / 20 °C View Scheme

1.1: (-)-Ipc2BH / tetrahydrofuran / 2 h / 0 °C 1.2: 1 h / 0 - 20 °C 2.1: lithium hydroxide hydrate / methanol / 24 h / 45 °C 2.2: pH 4 3.1: 2,3-dicyano-5,6-dichloro-p-benzoquinone / dichloromethane; water / 0.17 h / 0 °C 4.1: chloroformic acid ethyl ester; triethylamine / dichloromethane / 2 h / 0 °C 4.2: 2.5 h / 0 - 20 °C 5.1: cesium fluoride; methanol / 3 h / 20 °C View Scheme