oxalyl dichloride in dichloromethane 1.) 0 deg C, 1 h, 2.) 20 deg C, 1 h;

1: 82 percent / sodium hydroxide, water / 2 h / Heating 2: 100 percent / oxalyl chloride / CH2Cl2 / 1.) 0 deg C, 1 h, 2.) 20 deg C, 1 h View Scheme

T=20°C; 10 h;