A green catalyst-free concomitant air oxidation of DMSO and cumene to form methylsulfonylmethane (dimethylsulfone)

Abstract

Methylsulfonylmethane (MSM) is a newly discovered human nutrient that has significant health care and therapeutic function. In this work, we developed a new type of catalyst-free air oxidation of dimethyl sulfoxide (DMSO) to MSM under relatively mild conditions based on the mechanism of isopropylphenyl free radicals (R·) activating molecular oxygen (O₂) generating reactive oxygen species (ROS). Experimental results showed that cumene as a solvent, due to its active tertiary sp³ C–H bond, promotes the efficient catalyst-free air oxidation of DMSO to MSM under relatively mild optimized conditions. Based on the quenching test of free radicals and theoretical calculation of the activation energies of two oxidation pathways of isopropylphenyl peroxy radicals (ROO·) and cumene hydroperoxide (CHP), it has been demonstrated that ROS in this reaction is mainly ROO· and hydroxyl radicals (HO·). Furthermore, we proposed a possible catalyst-free air oxidation mechanism. This work provided a simple and cost-efficient approach for the green synthesis of MSM.

GRAPHICAL ABSTRACT

KEYWORDS:

• MSM
• DMSO
• air
• catalyst-free
• ROO

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

We acknowledge the financial support for this work by the National Natural Science Foundation of China [grant number 21073057], [grant number 21676079], the Natural Science Foundation of Hunan Province [grant number 11JJ6008], [grant number 2020JJ4425].