Multi-step reaction with 3 steps 1: 95 percent / p-toluenesulfonic acid / benzene / Heating2: 98 percent / lithium diisopropylamide / tetrahydrofuran / 2 h / -78 °C3: titanium tetrachloride / CH2Cl2 / 6 h / -78 °C  

Multi-step reaction with 4 steps 1: 1,4-diazabicyclo<2.2.2>octane2: 95 percent / p-toluenesulfonic acid / benzene / Heating3: 98 percent / lithium diisopropylamide / tetrahydrofuran / 2 h / -78 °C4: titanium tetrachloride / CH2Cl2 / 6 h / -78 °C