Studies on Pyrazines; Part 30:¹ Synthesis of Aminopyrazines from Azidopyrazines

Azidopyrazines do not undergo reduction by reagents that are effective for the preparation of alkyl- or arylamines from the azides because the heterocyclic azides exist in the bicyclic form of tetrazolo[1,5-a]pyrazines. Nevertheless, the conversion into aminopyrazines was achieved by hydrogenolysis in the presence of ammonium hydroxide and palladium-on-carbon or particularly by reduction with tin(II) chloride in methanolic hydrochloric acid, in 34-87% yields. To elucidate the successful progress of the reaction, the equilibrium of azide-tetrazole was examined by ¹H NMR spectroscopy in various solvents.