Simple and Friendly Sulfones Synthesis Using Aqueous Hydrogen Peroxide with a Reusable Keggin Molybdenum Heteropolyacid, Immobilized on Aminopropyl-Functionalized Silica

Abstract

Keggin molybdenum heteropolyacid (H₃PMo₁₂O₄₀), immobilized on aminopropyl-functionalized silica catalysts, were made using two immobilization methods: incipient wetness and equilibrium adsorption. The material prepared for the equilibrium adsorption technique was found to be a highly efficient, ecofriendly, and recyclable heterogeneous catalyst for the selective oxidation of sulfides to sulfones in excellent yields, under mild reaction condition using 35% w/v aqueous hydrogen peroxide as the oxidant.

Keywords:

• Functionalized silica
• hydrogen peroxide
• Keggin heteropolyacid
• sulfide oxidation

The authors thank Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional de Promoción Científica y Tecnológica, and Universidad Nacional de La Plata for financial support. GPR and PGV are members of CONICET.

Notes

^a H₂O₂: 0.75 mL, except Entry 13: 1 mL and Entry 14: 0.20 mL.

^b Yield% of pure product.

^c First reuse.

^d Second reuse.

^e Conversion of sulfide, 100%.

^a See Experimental section for reaction conditions.

^b We performed also the oxidation reaction at 25 °C with substrates sensitive to the oxidation. Double and triple bonds, alcohols, amines, aldehydes and esters as styrene, phenyl acetylene, undecene, phenyl allyl ether, 1-decanol, aniline and ethyl acetate are not oxidized if the reaction is carried out for 20 h at 25 °C. In this condition sulfide was oxidized selectively to sulfone using 1 mL of 35% w/v H₂O₂.

^c Pure product yields.

^d Turnover frequency (product mols × H₃PMo₁₂O₄₀ mols⁻¹ × h ⁻¹).

^e At 25°C.