water; tin(ll) chloride in ethanol 2 h; Reflux;

1: potassium acetate; acetic acid; bromine 2: aqueous Na2S2O4 View Scheme

1.1: sulfuric acid; nitric acid / 5.5 h / 10 - 20 °C 2.1: sulfuric acid / 20 - 90 °C 3.1: potassium acetate; acetic acid / 1 h / 20 °C 3.2: 20 °C 4.1: water; tin(ll) chloride / ethanol / 2 h / Reflux View Scheme

1.1: sulfuric acid / 20 - 90 °C 2.1: potassium acetate; acetic acid / 1 h / 20 °C 2.2: 20 °C 3.1: water; tin(ll) chloride / ethanol / 2 h / Reflux View Scheme

camphor-10-sulfonic acid 2 h; Reflux; Overall yield = 75 percent; Overall yield = 9.5 g;

acetic acid 2 h; Reflux; Overall yield = 52 percent; Overall yield = 15 g;

T=175 - 180°C; 1 h;

1: 3,4-diamino-5-bromopyridine; orthoformic acid triethyl ester With camphor-10-sulfonic acid 2 h; Reflux; 2: zink cyanide With tetrakis(triphenylphosphine) palladium(0) in N,N-dimethyl-formamide T=100°C; 2 h; Microwave irradiationInert atmosphere; Overall yield = 1.5 g;