Convenient access to new 4-substituted aminopyrido[2,3-d]pyrimidine derivatives

[Display omitted] We describe in this Letter, a novel series of pyrido[2,3-d]pyrimidines 6–11 derived from 3-cyano-2-aminopyridines 4a–f via formamidine formation 5a–f followed by selective nucleophilic addition, with different primary amines, under solvent-free conditions. The structures of the newly synthesized compounds are confirmed by spectral analysis. This new approach includes some important aspects such as mild reaction conditions, high yields, and environmentally friendly process. The operational simplicity of this synthetic route will offer an attractive alternative to the conventional methods.