Polystyrene and Silica Gel–Supported, AlCl₃-Catalyzed Preparation of Diaryl Sulfoxides from Arenes and Thionyl Chloride

Abstract

A simple, chemoselective, and efficient method has been developed for direct conversion of arenes to symmetrical diaryl sulfoxides using thionyl chloride in the presence of a catalytic amount of cross-linked polystyrene-supported aluminium chloride (Ps-AlCl₃) and silica gel–supported aluminium chloride (SiO₂-AlCl₃). These solid acid catalysts are stable and can be easily recovered and reused without appreciable change in their efficiency.

Keywords:

• Arene
• polystyrene
• silica gel
• sulfinylation
• sulfoxide

Acknowledgments

Dedicated to the memory of Professor Ahmad Banihashemi.

The author thanks the Research Council of Shahrekord University for partial support of this work.

Notes

^a The molar ratio of the arene: SOCl₂:Ps-AlCl₃ ¹ is 2:1.2:0.15 and for SiO₂-AlCl₃ ² is 2:1.2:0.1.

^b Yields refer to pure isolated products, and all sulfoxides prepared are known compounds and were characterized by comparison of their physical and spectral data with those of the authentic samples.

^a The molar ratio of Subs. 1:Subs. 2:SOCl₂ is 2:2:1.1.

^b All reactions were carried out in CH₂Cl₂ at room temperature in the presence of Ps-AlCl₃ (0.15 mmol),¹ SiO₂-AlCl₃ (0.1 mmol),² and AlCl₃ (0.32 mmol).³

^c GC yield.

^a Tungstophosphoric acid (heteropoly acid).

^b 1-Butyl-3-methylimidazolium chloroaluminate (ionic liquid).