1: Et3N, oxalyl chloride, dimethylformamide / 1,2-dimethoxy-ethane / 0.67 h / -30 - 0 °C 2: diethyl ether / 1 h / -23 - 0 °C 3: 65 percent / 1.0 N aq. NaOH / methanol / 0.5 h / Ambient temperature View Scheme