Regioselective copper(I)-catalyzed ullmann amination of halopyridyl carboxylates using sodium azide: a route for aminopyridyl carboxylates and their transformation to pyrido[2, 3-d]pyrimidin-4(1H)-ones

We report herein an efficient, straightforward and ligand free synthesis of aminopyridyl carboxylates, an important building block used in pharmaceuticals and agrochemicals. The C(sp2)-N bond formation utilize a readily available Cu-catalyst, NaN3 as the amino source in ethanol, and the corresponding ortho-functionalized aromatic amines were synthesized in good to excellent yields. This ligand free one-pot domino methodology proceeds through Ullmann-type coupling of halopyridyl carboxylates with sodium azide followed by reduction with ethanol. These functionalized aminopyridyl carboxylates provides an easy access to biologically potent pyrido[2, 3-d]pyrimidin-4(1H)-one hybrids.