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Minute-scale, solvent-free microwave-assisted three-component synthesis of naphtho[1,2-e][1,3]oxazin-3-ones catalyzed by a recyclable Brønsted-Lewis acidic COF

Year: 2025

Type: article

Abstract: We report a bifunctional Brønsted–Lewis acidic covalent organic framework catalyst, Cu(II)/TFPOTDB–SO 3 H, that enables the solvent-free, microwave-assisted three-component synthesis of naphtho[1,2-e][1,3]oxazin-3-ones from aromatic aldehydes, β-naphthol, and urea. Under optimized conditions (0.01 g catalyst, 180 W), a broad range of electron-donating and electron-withdrawing substituents delivers the target products in 93–99 % isolated yields within 2–4 min. The catalyst is demonstrably heterogeneous (hot-filtration test halts conversion) with negligible Cu leaching (≤ 0.05 ppm), maintains morphology and uniform Cu(II) distribution (∼ 6.6 wt%) as shown by SEM/EDS, and preserves high activity over five recycles. Compared with prior systems, Cu(II)/ TFPOTDB–SO 3 H offers markedly shorter reaction times at higher yields under greener conditions. A cooperative mechanism is proposed in which –SO 3 H groups protonate the carbonyl while Cu(II) coordination further polarizes it, accelerating C–N/C–O bond formation. Thus, the engineered sulfonated COF operates as a robust, recyclable designer catalyst, translating synergistic –SO 3 H/Cu(II) chemistry into minute-scale, high-yield synthesis of privileged 1,3-oxazine scaffolds.

Source: Results in Chemistry

DOI: 10.1016/j.rechem.2025.102940

Authors: Forough Jafari, Farid Moeinpour, Fatemeh S. Mohseni-Shahri

Institution: Islamic Azad University Bandar Abbas

Language: English

Topic: Multicomponent Synthesis of Heterocycles

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,870

Funder: Islamic Azad University