sulfuric acid; water T=110°C; 22 h;

thionyl chloride T=60°C; 3 h; Cooling with ice;

1: With thionyl chloride T=0 - 20°C; 72.5 h; 2: With sodium hydrogencarbonate in water

1.1: p-toluenesulfonyl chloride / pyridine / 1 h / 0 °C 1.2: 0.25 h 2.1: methanol / 1.5 h / 25 °C View Scheme

1: 3,5-difluoropyridine-2-carboxylic acid With hydrogenchloride; oxalyl dichloride; N,N-dimethyl-formamide in 1,4-dioxane; dichloromethane T=20°C; 2 h; 2: 2-methylamino-ethanol With triethylamine in dichloromethane T=20°C; 20 h;