Convenient Synthesis of 2-Amino-1,8-naphthyridines, Building Blocks for Host-Guest and Self-Assembling Systems

Application of the Reimer-Tiemann reaction to 2,6-diaminopyridine afforded a 26% yield of 2,6-diaminopyridine-3-carboxaldehyde (4) and a small amount (4%) of 2,6-diaminopyridine-3,5-dicarboxaldehyde. Alternatively, conversion of 2,6-diaminopyridine to 2,6-bis(pivaloylamino)pyridine (6), directed lithiation with n-butyllithium, treatment with N-formylmorpholine, and hydrolysis produced 4 in 67% overall yield. The Friedländer condensation of 4 with a variety of activated and unactivated ketones afforded 2-amino-1,8-naphthyridines and bis(2-amino-1,8-naphthyridines) in moderate to good yields, providing a convenient synthesis of useful building blocks for new host-guest and self-assembling systems.