1.1: caesium carbonate / 4 h / 0 - 20 °C 2.1: -15 °C 3.1: trifluoroacetic acid / toluene / 4 h / 20 °C 4.1: oxalyl dichloride; N,N-dimethyl-formamide / toluene / 0.33 h / 20 °C 5.1: trimethylsilylazide / toluene / 0.33 h / 20 °C 6.1: acetic acid / 48 h / 20 °C 7.1: chloro-trimethyl-silane; zinc / ethanol / 70 °C 7.2: 0 °C 8.1: potassium carbonate / 20 °C View Scheme