Sulfolenes As Sustainable Substitutes for Dimethyl Sulfoxide

Dimethyl sulfoxide (DMSO) is a widely used solvent for chemical manufacturing processes; however it often involves energy intensive product purification methods.  Recovery of the solvent is cost prohibitive, resulting in large amounts of DMSO containing waste streams that often times have to be incinerated.  Sulfolenes have similar solvent properties as DMSO, but in contrast, can be easily removed and recycled.   In fact, upon mild heating (110 to 135 °C), sulfolenes undergo a retro-cheletropic reaction yielding sulfur dioxide and the corresponding diene; these two volatile products are easily recombined to reform and recycle the solvent.

Some examples of chemical processes effectively carried in piperylene sulfone and/or butadiene sulfone include nucleophilic substitution reactions, copper catalyzed oxidation of alcohols and hydrolysis of β-pinene.  For all cases, the “built in” switchability of the solvent was exploited to enhance the production scheme involving efficient reaction and facile separation.  Process improvements include in-situ acid catalysis, facile product purification, efficient catalyst and solvent recovery schemes, etc.

In this presentation we will review the advances done in developing sustainable processes using switchable sulfolene solvents as substitutes for DMSO.   A scope of their applications will be discussed in comparison with traditional dipolar, aprotic solvents such as DMSO.  Moreover, details will be provided regarding solvent recovery methods and recyclability.