Direct access to 4-carboxy-1,8-naphthyridines and related compounds through Pfitzinger-type chemistry

The 4-carboxy-1,8-naphthyrid-2-yl moiety is a useful ligand component in that it promotes lower energy electronic absorption in its metal complexes and also provides a useful tether for anchoring the ligand to a semiconductor surface. The synthon [2-(pivaloylamino)pyrid-3-yl]oxoacetic acid ethyl ester can be easily obtained in two steps from 2-aminopyridine. The Pfitzinger-type condensation of this molecule with a 2-acetylazaaromatic species in ethanolic KOH, after acidification, directly provides bi- and tridentate ligands containing the 4-carboxy-1,8-naphthyrid-2-yl moiety.