sodium hydroxide; tetra(n-butyl)ammonium hydrogensulfate in tetrahydrofuran; water T=20°C; 24 h;

1: dichloromethane / 15 h / 0 - 20 °C / |Inert atmosphere 2: triphenylphosphine; di-isopropyl azodicarboxylate / toluene / 3 h / 60 °C / |Inert atmosphere 3: dimethylsulfide; aluminum tri-bromide / dichloromethane / 5.5 h / 5 - 10 °C / |Inert atmosphere 4: (benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; N-ethyl-N,N-diisopropylamine / N,N-dimethyl-formamide / 18 h / 20 °C / |Inert atmosphere 5: tris(dimethylamino)-sulphonium difluorotrimethylsilicate / N,N-dimethyl-formamide / 4.5 h / 0 °C / |Inert atmosphere View Scheme