Sulfonylation reactions photocatalyzed by quantum dots: rule of band-position and surface chemistry

• Published in: Catalysis science & technology 2023-04, Vol.13 (8), p.2377-2384
• Main Authors: Costa, Jadielson, Galdino, Danilo, Sousa, Felipe L, Freitas, Denilson V, Jardim, Paula M, Menezes, Paulo H, Navarro, Marcelo
• Format: Article
• Language: English
• Subjects: Benzyl bromide; Catalytic activity; Conduction bands; Cysteamine; Excitons; Halides; Molecular orbitals; Oxidation; Photocatalysis; Photoexcitation; Quantum dots; Reagents; Sodium salts; Sulfones; Valence band
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d3cy00059a

An environmentally friendly methodology for the synthesis of different functionalized sulfones is described here. Quantum dots (QDs) of cysteamine (Cys) or 3-mercaptopropionic acid (MPA) capped cadmium chalcogenides (CdY, Y = S, Se, Te) were used as photocatalyst (UV, λ = 365 nm) for sulfonylation reactions. The reaction between benzyl bromide and sodium p -toluenesulfinate was used to determine the ideal experimental conditions, where CdSe-Cys presented the best photocatalytic activity, and the sulfonylation product was isolated in 4% to 92% yields. The optimized reaction conditions were then applied on reactions of benzyl, allyl, alkyl, aryl halides and α-bromoesters using different sodium salts of sulfinic acids and the products where obtained in a 57% to 99% yield range after 2 to 8 hours. A mechanism proposal involves the simultaneous reduction/oxidation of the reagents by the exciton generated by photoexcitation of the QDs. The photocatalytic activity of the QDs was estimated by analysis of the conduction/valence band energies and correlated with LUMO/HOMO energies of the reagents. Cyclic voltammetry was used as an analytical tool. An environmentally friendly methodology for the synthesis of different functionalized sulfones is described here.