1: 41 percent / boron trifluoride etherate/molecular sieve 4A / toluene / 25 h / Heating 2: 72 percent / tetrahydrofuran / RT, 1h; 40 deg C, 1 h; reflux, 2 h 3: 72 percent / potassium hydroxide / ethane-1,2-diol / 6 h / Heating View Scheme