Phosphonic acid tagged carbon quantum dots encapsulated in SBA-15 as a novel catalyst for the preparation of N-heterocycles with pyrazolo, barbituric acid and indole moieties.

Herein, we have presented a new insight for the synthesis of a hybrid heterogeneous catalyst. For this purpose, phosphonic acid tagged carbon quantum dots of CQDs-N(CH2PO3H2)2 encapsulated and assembled in channels of SBA-15 using a post-modification strategy. The mesoporous catalyst of functionalized carbon quantum dots (CQDs) was characterized by several techniques. CQDs-N(CH2PO3H2)2/SBA-15 as an excellent catalyst was applied for the preparation of novel pyrazolo[4',3':5,6]pyrido[2,3-d]pyrimidine derivatives by using pyrazole, barbituric acid and indole moieties at 100 °C under the solvent-free condition. The present work shows that a significant increase in the catalytic activity can be achieved by a rational design of mesoporous SBA-15 modified with CQDs for the synthesis of biological active candidates. The synthesized compounds did not convert to their corresponding pyridines via an anomeric-based oxidation mechanism.