1: With lithium diisopropyl amide in tetrahydrofuran T=-78°C; 2: With 1,2-di-iodoethane T=-78 - 20°C;

1.1: 100 percent / NBS / dimethylformamide / 24 h / 20 °C 2.1: n-BuLi / tetrahydrofuran; hexane / 1.17 h / -78 °C 2.2: tetrahydrofuran; hexane / -70 - 0 °C 3.1: aq. H2O2 / methanol / 1 h / 20 °C 4.1: t-BuLi / pentane; tetrahydrofuran / 3.5 h / -100 - -70 °C 4.2: I2 / pentane; tetrahydrofuran / 2 h / -70 - 0 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 1.17 h / -78 °C 1.2: tetrahydrofuran; hexane / -70 - 0 °C 2.1: aq. H2O2 / methanol / 1 h / 20 °C 3.1: t-BuLi / pentane; tetrahydrofuran / 3.5 h / -100 - -70 °C 3.2: I2 / pentane; tetrahydrofuran / 2 h / -70 - 0 °C View Scheme

1.1: aq. H2O2 / methanol / 1 h / 20 °C 2.1: t-BuLi / pentane; tetrahydrofuran / 3.5 h / -100 - -70 °C 2.2: I2 / pentane; tetrahydrofuran / 2 h / -70 - 0 °C View Scheme

1.1: Cu / dimethylformamide / 4 h / 140 °C 2.1: (+)-O,O-dibenzoyltartaric acid / CH2Cl2 2.2: aq. CH2Cl2 / CH2Cl2 / 0.5 h 3.1: 91 percent / NBu3; HSiCl3 / xylene / 140 °C View Scheme