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

摘要

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 m(2) g(-1), and was recycled 5 times without loss of activity.