A novel, facile, rapid, solvent free protocol for the one pot green synthesis of chromeno[2,3-d]pyrimidines using reusable nano ZnAl2O4 – a NOSE approach and photophysical studies

Abstract

The current protocol resulted in the preparation of an eco-friendly, highly stable, reusable nano ZnAl₂O₄ and for the first time this was used as an excellent catalyst for the pseudo four component synthesis of a library of fluorescent chromeno[2,3-d]pyrimidine derivatives. This novel protocol involved the grinding of salicylaldehydes, malononitrile and secondary amines in the presence of a catalytic amount of nano ZnAl₂O₄ at room temperature which was an extremely simple, facile, cost effective, solvent free protocol and also required just two minutes to achieve the products with excellent yields. The synthesized chromeno[2,3-d]pyrimidine derivatives showed significant absorption and emission properties and large Stoke's shift values due to their characteristic feature of an excited state intramolecular proton transfer (ESIPT) mechanism. Nano ZnAl₂O₄ exhibited better catalytic activity than that of the bulk due to its larger surface area of 63 m² g⁻¹, and was recycled 5 times without loss of activity.