A New Efficient One‐Pot Three‐Component Synthesis of Diverse Pyrido[1,2‐a]pyrimidines

The pyrido[1,2‐ a ]pyrimidine scaffold has great potential for the creation of bioactive substances. Here we propose a simple, cost‐effective, efficient approach to forming this core based on a one‐pot three‐component reaction of commercially available 3‐oxo esters, α,β‐unsaturated aldehydes and 1,3‐diaminopropane. The developed strategy makes it possible to obtain diverse pyrido[1,2‐ a ]pyrimidines thanks to alternative intramolecular cyclization pathways that depend on the substituent in the 3‐oxo ester. Their diastereomeric structure was determined using NMR spectroscopy and XRD. A mechanism for the formation of new pyrido[1,2‐ a ]pyridines has been proposed.