boron tribromide in dichloromethane T=-35 - 0°C;

1.1: n-BuLi / tetrahydrofuran; pentane / 0.67 h / -78 °C 1.2: 78 percent / tetrahydrofuran; pentane / 1.25 h / cooling 2.1: 85 percent / boron tribromide / CH2Cl2 / -35 - 0 °C View Scheme

1.1: 85 percent / aluminum chloride / 1,2-dichloro-benzene / 6 h / 83 °C 2.1: 82 percent / KOH; hydrazine monohydrate / triethylene glycol / 90 - 200 °C 3.1: 75 percent / polyphosphoric acid / 1 h / 80 °C 4.1: p-toluenesulfonic acid monohydrate; trimethyl orthoformate / methanol; benzene / 40 h / Heating 4.2: 75 percent / p-toluenesulfonic acid monohydrate / benzene / 4 h / Heating 5.1: n-BuLi / tetrahydrofuran; pentane / 0.67 h / -78 °C 5.2: 78 percent / tetrahydrofuran; pentane / 1.25 h / cooling 6.1: 85 percent / boron tribromide / CH2Cl2 / -35 - 0 °C View Scheme

1.1: p-toluenesulfonic acid monohydrate; trimethyl orthoformate / methanol; benzene / 40 h / Heating 1.2: 75 percent / p-toluenesulfonic acid monohydrate / benzene / 4 h / Heating 2.1: n-BuLi / tetrahydrofuran; pentane / 0.67 h / -78 °C 2.2: 78 percent / tetrahydrofuran; pentane / 1.25 h / cooling 3.1: 85 percent / boron tribromide / CH2Cl2 / -35 - 0 °C View Scheme

1.1: 75 percent / polyphosphoric acid / 1 h / 80 °C 2.1: p-toluenesulfonic acid monohydrate; trimethyl orthoformate / methanol; benzene / 40 h / Heating 2.2: 75 percent / p-toluenesulfonic acid monohydrate / benzene / 4 h / Heating 3.1: n-BuLi / tetrahydrofuran; pentane / 0.67 h / -78 °C 3.2: 78 percent / tetrahydrofuran; pentane / 1.25 h / cooling 4.1: 85 percent / boron tribromide / CH2Cl2 / -35 - 0 °C View Scheme

1.1: 82 percent / KOH; hydrazine monohydrate / triethylene glycol / 90 - 200 °C 2.1: 75 percent / polyphosphoric acid / 1 h / 80 °C 3.1: p-toluenesulfonic acid monohydrate; trimethyl orthoformate / methanol; benzene / 40 h / Heating 3.2: 75 percent / p-toluenesulfonic acid monohydrate / benzene / 4 h / Heating 4.1: n-BuLi / tetrahydrofuran; pentane / 0.67 h / -78 °C 4.2: 78 percent / tetrahydrofuran; pentane / 1.25 h / cooling 5.1: 85 percent / boron tribromide / CH2Cl2 / -35 - 0 °C View Scheme