1.1: oxalyl dichloride / N,N-dimethyl-formamide / acetonitrile / 4.5 h / 0 - 40 °C / Inert atmosphere 2.1: titanium tetrachloride / dichloromethane / 4 h / 0 - 40 °C / Inert atmosphere 3.1: triethylsilane; titanium tetrachloride / dichloromethane / 0 - 20 °C / Inert atmosphere 3.2: N,N-dimethylaminopyride / 24 h / 20 °C 4.1: sodium methylate / methanol / 0.5 h / 20 °C 4.2: 4 h / 80 °C 4.3: 1 h / 50 °C View Scheme