1: With n-butyllithium in tetrahydrofuran; hexane T=-78 - -65°C; 2: With boric acid trimethyl ester in tetrahydrofuran; hexane T=-65 - 20°C; 3: With hydrogenchloride in tetrahydrofuran; hexane T=20°C; Further stages.;

1.1: 84.6 percent / Na2CO3; Br2 / 1,2-dichloro-ethane / 50 °C 2.1: 83.8 percent / NaOH / H2O; ethanol / 6 h / Heating 3.1: sodium hydroxide / ethanol; H2O / Heating 4.1: n-BuLi / tetrahydrofuran; hexane / -78 - -65 °C 4.2: B(OCH3)3 / tetrahydrofuran; hexane / -65 - 20 °C 4.3: aq. HCl / tetrahydrofuran; hexane / 20 °C View Scheme

1.1: 86 percent / Sulfuric acid / 3 h / 60 °C 2.1: 84.6 percent / Na2CO3; Br2 / 1,2-dichloro-ethane / 50 °C 3.1: 83.8 percent / NaOH / H2O; ethanol / 6 h / Heating 4.1: sodium hydroxide / ethanol; H2O / Heating 5.1: n-BuLi / tetrahydrofuran; hexane / -78 - -65 °C 5.2: B(OCH3)3 / tetrahydrofuran; hexane / -65 - 20 °C 5.3: aq. HCl / tetrahydrofuran; hexane / 20 °C View Scheme

1.1: sodium hydroxide / ethanol; H2O / Heating 2.1: n-BuLi / tetrahydrofuran; hexane / -78 - -65 °C 2.2: B(OCH3)3 / tetrahydrofuran; hexane / -65 - 20 °C 2.3: aq. HCl / tetrahydrofuran; hexane / 20 °C View Scheme

1.1: 83.8 percent / NaOH / H2O; ethanol / 6 h / Heating 2.1: sodium hydroxide / ethanol; H2O / Heating 3.1: n-BuLi / tetrahydrofuran; hexane / -78 - -65 °C 3.2: B(OCH3)3 / tetrahydrofuran; hexane / -65 - 20 °C 3.3: aq. HCl / tetrahydrofuran; hexane / 20 °C View Scheme