oxalyl dichloride; N,N-dimethyl-formamide in dichloromethane T=0 - 20°C; 4 h;

1: 85 percent / t-BuOK / 2-methyl-propan-2-ol; 1,2-dimethoxy-ethane / 3 h / Ambient temperature 2: 97 percent / NaOH / ethanol; H2O / 5 h / Heating 3: oxalyl chloride / CH2Cl2 / 0 deg c, 4 h, then rt., 1 h View Scheme

1: 97 percent / NaOH / ethanol; H2O / 5 h / Heating 2: oxalyl chloride / CH2Cl2 / 0 deg c, 4 h, then rt., 1 h View Scheme