Catalytic amination of 5-substituted pyridines with hydrazine derivatives

[GRAPHICS] Protected pyridylhydrazine derivatives were prepared in a one-step palladiu m-catalyzed amination reaction using chelating phosphine ligands, 2-Pyridyl chlorides, bromides, and triflates were effective electrophiles in these r eactions, Di-tert-butyl hydrazodiformate was an excellent hydrazine substra te, and the resulting products were deprotected under mild conditions. Cata lytic amination provides a direct route to protected bifunctional hydrazino pyridine linkers that are suitable for metal-bioconjugate syntheses.