1: 3-bromo-5-pyridine-carboxylic acid With 2,2,6,6-tetramethyl-piperidine; n-butyllithium in tetrahydrofuran; hexane T=-50°C; 0.5 h; 2: carbon dioxide in tetrahydrofuran; hexane 3: With hydrogenchloride in water pH=3;

potassium permanganate T=50 - 60°C;

1: CuSO4; aqueous NH3 / 200 °C 2: nitrosylsulfuric acid; H2O / 80 °C / Ueber das Diazoniumsulfat View Scheme