oxalyl dichloride; dimethyl sulfoxide; triethylamine in dichloromethane T=-78 - 20°C;

2,4,6-trichloro-1,3,5-triazine; N,N-dimethyl-formamide; sodium bromide in dichloromethane T=25°C; 0.5 h;

thionyl chloride in N,N-dimethyl-formamide

1.1: 91 percent / oxalyl chloride; DMSO; Et3N / CH2Cl2 / -78 - 20 °C 2.1: 98 percent / p-TsOH / 12 h / Heating 3.1: 76 percent / O2; 5,10,15,20-tetrakis(pentafluorophenyl)porphine / CDCl3 / 6 h / -35 °C / Irradiation 4.1: L-methionine / acetonitrile; H2O / 0.25 h / 0 °C 4.2: 41 percent / NaBH4; DBU / tetrahydrofuran; H2O / 0.25 h / 0 °C View Scheme