A PANI-Fe3O4@ZnO nanocomposite: a magnetically separable and applicable catalyst for the synthesis of chromeno-pyrido[ d]pyrimidine derivatives

Abstract

We report herein green, practical, PANI-Fe₃O₄@ZnO-nanocomposite-catalyzed cyclocondensation reactions involving 4-aminocoumarin, 1,3-dimethylbarbituric acid, and aromatic aldehydes in an aqueous medium at room temperature to synthesize 9,11-dimethyl-7-aryl-6H-chromeno[3',4':5,6]pyrido[2,3-d]pyrimidine-6,8,10(9H,11H)triones. This research aims to provide an applicable and high-yield protocol that follows the principles of green chemistry, with the use of water as an environmentally benign medium and the PANI-Fe₃O₄@ZnO nanocomposite as a magnetically recoverable catalyst.

Scheme 1. The synthesis of 9,11-dimethyl-7-aryl-6H-chromeno[3′,4′:5,6]pyrido[2,3-d]pyrimidine-6,8,10(9H,11H)trione derivatives.

Fig. 1. The reusability of the catalyst.

Fig. 2. The XRD pattern of the synthesized PANI-Fe₃O₄@ZnO nanocomposite.

Fig. 3. An SEM image of the synthesized PANI-Fe₃O₄@ZnO nanocomposite.

Fig. 4. A TEM image of the synthesized PANI-Fe₃O₄@ZnO nanocomposite.

Fig. 5. The EDX spectrum of the synthesized PANI-Fe₃O₄@ZnO nanocomposite.

Scheme 2. The synthesis of 9,11-dimethyl-7-(4-chlorophenyl)-6H-chromeno[3′,4′:5,6]pyrido[2,3-d]pyrimidine-6,8,10(9H,11H)trione (4c).

Scheme 3. The proposed mechanism for the formation of 4.