1: 1.) NaH / 1.) THF, 0 deg C, 1 h, 2.) reflux, 12-20 h 2: 1.) ozone, 2.) dimethyl sulfide / 1.) dichloromethane, -78 deg C, 2.) -78 deg C to room temperature, 2-3 h, then room temperature, 12 h View Scheme

oxalyl dichloride; TEA; dimethyl sulfoxide in tetrahydrofuran; dichloromethane T=-60°C; 0.5 h;

1: 92 percent / 4-(Dimethylamino)pyridine (DMAP) / diethyl ether / 1.) -20 deg C, 30 min, 2.) 15 h, room temperature 2: 58 percent / 2 h / 200 °C View Scheme