An efficient synthesis of novel tricyclic fused pyrido[3,2-<i>e</i>]thiazolo[3,2-<i>a</i>]pyrimidines <i>via</i> one-pot three-component reaction in a green media

In this study, we report the development of an efficient and facile synthetic approach for the preparation of novel pyrido[3,2-e]thiazolo[3,2-a]pyrimidines via a tandem Knoevenagel–Michael cyclo-condensation reaction. This transformation employs heterocyclic enamine, aromatic aldehydes, and malononitrile in the presence of DABCO as an organocatalyst under ethanol reflux conditions. The reactions proceed to completion within 1.0–1.5 h, affording the desired products in good to high yields (75%–82%). The main goal of this study is to design and synthesize heterocyclic scaffolds that exhibit promising biological activity. Notable benefits of this approach include a simple work-up procedure, environmentally friendly conditions, and the use of an inexpensive and readily accessible catalyst. The structures of the target compounds (<b>4a–j</b>) were validated using IR, ¹H, and ¹³C NMR spectroscopy, mass spectrometry, and elemental analysis, demonstrating the effectiveness and practicality of the method developed.