The Sustainable and Scalable Synthesis of Piperylene Sulfone: A “Volatile” and Recyclable DMSO Substitute

We have established a roadmap to a sustainable and scalable synthesis of piperylene sulfone (PS), a potentially important new dipolar aprotic solvent. PS is a fully recyclable solvent with solvatochromic properties similar to dimethyl sulfoxide (DMSO). Although DMSO is an important and powerful polar, aprotic solvent for conducting chemical reactions, the separation of the reaction products from the solvent is difficult and expensive. In contrast, PS can be decomposed by undergoing a reversible retro-cheletropic reaction at 110ºC, permitting facile solvent removal and recycle. Because PS is not commercially available, we synthesized laboratory quantities using a method not optimized to scale-up due to expensive chemicals and significant waste generation. In order to develop and optimize a scalable process, we first determined the kinetic parameters associated with the reaction by employing in-situ proton NMR measurements and then studied the effects of radical inhibitors in reducing unwanted side reactions. In addition, we have now recovered PS from the reaction mixture via a sustainable carbon dioxide separation method, which resulted in a substantial waste reduction. Thus, we have developed a cost-effective, safe, and sustainable scale-up method for PS, a “volatile” and recyclable DMSO substitute.