boron trifluoride in dichloromethane T=-20°C;

1: oxalyl chloride / benzene / 23 °C 3: 92 percent / boron trifluoride / CH2Cl2 / -20 °C View Scheme

2: 92 percent / boron trifluoride / CH2Cl2 / -20 °C View Scheme

triethylamine in tetrahydrofuran; methanol T=20°C; 16 h;

1: 83 percent / hexane / 72 h / 20 °C 2: 67 percent / 1,8-diazabicyclo[5.4.0]undec-7-ene; AgCl / CH2Cl2 / 25 h / Heating 3: 100 percent / silica gel / CH2Cl2; hexane View Scheme

1: 83 percent / hexane / 72 h / 20 °C 2: 67 percent / 1,8-diazabicyclo[5.4.0]undec-7-ene; AgCl / CH2Cl2 / 25 h / Heating 3: 100 percent / silica gel / CH2Cl2; hexane 4: 85.4 percent / diisobutylaluminum hydride / toluene / 0.38 h / -70 - -65 °C View Scheme