1: 1,8-diazabicyclo[5.4.0]undec-7-ene / 3.5 h / 140 - 160 °C 2: sodium hydroxide; ethanol View Scheme

1.1: 1,8-diazabicyclo[5.4.0]undec-7-ene / 3.5 h / 140 - 160 °C 2.1: sodium hydroxide; ethanol 3.1: oxalyl dichloride / N,N-dimethyl-formamide / dichloromethane / 17 h / 0 - 20 °C 4.1: n-butyllithium / tetrahydrofuran; hexanes / -70 - -10 °C / Inert atmosphere 4.2: 3 h / -60 - 0 °C View Scheme

1: 1,8-diazabicyclo[5.4.0]undec-7-ene / 3.5 h / 140 - 160 °C 2: sodium hydroxide; ethanol 3: oxalyl dichloride / N,N-dimethyl-formamide / dichloromethane / 17 h / 0 - 20 °C View Scheme