Synthesis of MCM-41 Supported L-proline Copper (I) Complex and Its Catalytic Performance for the Coupling Reaction of p-Iodotoluene with Sodium Methanesulfinate

Abstract

By sequentially condensing 3-chloropropyltrimethoxysilane and trimethylchlorosilane with MCM-41 in toluene, chloropropyl-functionalized MCM-41 (MCM-41-Cl) is obtained. L-proline sodium functionalized MCM-41 (MCM-41-L-Proline) is successfully prepared by condensation and immobilization of MCM-41-Cl with N-Boc-4-hydroxy-L-proline, followed by deprotection of Boc and acid-base neutralization reaction. The performance of MCM-41-L-Proline in catalyzing the coupling reaction of p-iodotoluene (PIT) with sodium methanesulfinate (CH3SO2Na) is investigated with the synergistic effect of CuI. The results indicate that, under optimized reaction conditions, the MCM-41-L-Proline/CuI catalytic system delivers a 48.5% yield of methylsulfonyl toluene (MST). Interestingly, FT-IR results indicate that MCM-41-L-Proline and CuI in situ formed the MCM-41-L-Proline Cu(I) complex during the coupling reaction. This catalyst demonstrates excellent catalytic stability and recyclability, maintaining its activity with no significant decline after six cycles.

Introduction

This study focuses on the development of a heterogeneous Cu(I)-based catalytic system for the synthesis of sulfone compounds via cross-coupling reactions. Sulfones are important functional molecules widely used in pharmaceuticals, agrochemicals, materials science, and organic synthesis. Traditional methods for sulfone synthesis include sulfide oxidation, Friedel–Crafts sulfonylation, and transition-metal-catalyzed coupling. Among these, transition metal-catalyzed coupling offers superior functional group tolerance and flexibility, but homogeneous catalytic systems often face challenges in catalyst recovery and reuse.

To overcome these limitations, the authors designed a heterogeneous catalyst by immobilizing L-proline onto mesoporous MCM-41 silica, forming MCM-41-L-Proline. This material acts as a support for CuI, generating an active L-proline–Cu(I) complex in situ during the reaction. The catalyst was applied to the coupling reaction between aryl iodides (e.g., p-iodotoluene) and sodium methanesulfinate (CH?SO?Na) to produce methylsulfonyl toluene (MST).

Catalyst Preparation

MCM-41 was synthesized and functionalized with chloropropyl groups, followed by grafting of N-Boc-L-hydroxyproline. After Boc deprotection and alkaline treatment, L-proline-functionalized MCM-41 (MCM-41-L-Proline) was obtained, with a grafting density of 0.925 mmol/g. The catalyst structure was confirmed using XRD, FT-IR, and elemental analysis. Characterization results demonstrated that:

• The ordered hexagonal mesoporous structure of MCM-41 was retained after functionalization and multiple catalytic cycles.

• FT-IR spectra confirmed successful immobilization of L-proline and coordination with Cu(I) during reaction.

• The catalyst structure remained stable after seven reuse cycles.

Catalytic Performance

The catalytic activity of the MCM-41-L-Proline/CuI system was optimized by examining key reaction parameters. Optimal conditions were determined as:

• Reaction temperature: 373 K

• CH?SO?Na/PIT molar ratio: 1.2

• CuI dosage: 15 mol%

• MCM-41-L-Proline dosage: 20 mol%

• DMSO volume: 5 mL

• Reaction time: 24 h

Under these optimized conditions, the yield of MST reached 48.5%. The catalyst could be recycled up to seven times with minimal structural degradation, demonstrating good stability and reusability.

Conclusion

In summary, through a series of condensation reactions, L-hydroxyproline was successfully immobilized on MCM-41, and MCM-41-L-Proline was further obtained by acid-base neutralization reaction. The effects of reaction temperature, CH3SO2Na/PIT molar ratio, CuI dosage, DMSO dosage, MCM-41-L-Proline dosage and reaction time on the coupling reaction were investigated, and the suitable reaction conditions were obtained. Under optimized reaction conditions, the MCM-41-L-Proline/CuI catalytic system delivered a 48.5% yield of MST. FT-IR results indicate that MCM-41-L-Proline Cu(I) was prepared in situ between MCM-41-L-Proline and CuI during the coupling reaction. After six cycles, MCM-41-L-Proline Cu(I) still delivered a favorable yield of MST (47.5%) without deactivation. XRD and FT-IR results indicated that the mesoporous structure and composition of the MCM-41-L-Proline Cu(I) catalyst remained well-preserved after the recycling tests, indicating that the sample had good catalytic stability and recycling performance.

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Copyright

Copyright © 2026 Xiaorong Xiang, Huiqing Cheng, Qian Chen, Xiang Li, Feng Wu, Xiaoxue Liu, Hao Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.