Copper(I)-Catalyst-Free Approach for the Synthesis of Chromene-Fused Pyrido[3,2-d]pyrimidines by Lewis Acid Catalyzed Aza-Diels-Alder Reaction

Pyrido[3,2-d]pyrimidine derivatives have been synthesized by the hetero-Diels-Alder reaction of 5-amino-1,3-dimethyl uracil and O-propargylated salicylaldehyde. The reaction requires only a single-step operation and provides potentially bioactive polycyclic heterocycles in high yields (71-82%) from easily available starting materials.