1: boron trifluoride diethyl etherate; magnesium sulfate / dichloromethane / 1 h / -40 °C / Inert atmosphere 2: 2,6-dimethylpyridine / dichloromethane / 20 °C 3: dilithium tetrachlorocuprate / tetrahydrofuran / 3 h / 20 °C 4: tetrabutyl ammonium fluoride / tetrahydrofuran / 0.5 h / 20 °C View Scheme

With  boron tribromide in  dichloromethane; 1,2-dichloro-ethane 1.5 h;  Reflux;