1.1: n-BuLi / tetrahydrofuran / 0.5 h / -78 °C 1.2: N-fluorobenzenesulphonimide / tetrahydrofuran / 12 h / 20 °C 1.3: 47 percent / acetic acid; tetrahydrofuran; H2O / 12 h / 60 °C 2.1: 98 percent / DMSO; oxalyl chloride; Et3N / CH2Cl2 / 1 h / -78 - -45 °C View Scheme