1.1: 72 percent / BBr3 / CH2Cl2 / 40 °C 2.1: 82 percent / 220 °C 3.1: 65 percent / NaH / dimethylformamide 4.1: iPrMgCl / tetrahydrofuran / 2 h / -20 °C 4.2: tetrahydrofuran / 16 h / -20 - 22 °C 4.3: 72 percent / TFA / CH2Cl2 / 2 h / 22 °C View Scheme

boron tribromide in dichloromethane T=40°C;