Piperylene Sulfone: A Recyclable Substitute for Dimethyl Sulfoxide

Piperylene sulfone is presented as a separable and recyclable dipolar, aprotic solvent substitute for dimethyl sulfoxide (DMSO). DMSO is a dipolar, aprotic solvent often used in industry for conducting chemical reactions. However, DMSO presents several challenges in terms of product isolation and separation. Its relatively high boiling point and product dependent separation leads to costly and inefficient recycling strategies. Piperylene sulfone has similar solvatochromic properties to DMSO but unlike DMSO, which has a melting point of 19 °C, piperylene sulfone has a melting point of -12 °C. At 110 °C, piperylene sulfone decomposes into 1,3-pentadiene and sulfur dioxide; these volatile compounds are captured and recombined to reform piperylene sulfone, which is the recycled to the reactor. For example, the nucleophilic substitution reaction of benzyl chloride and potassium thioacetate, to yield benzyl thiocetate, takes place in piperylene sulfone at comparable rates than in DMSO.  The second order rate constants were greater than 1800 mL mol^-1 s^-1. Once the reaction is complete, the reaction mixture is heated to 110 °C, where the solvent decomposes leaving only the product in the reactor. After recombination eighty-seven percent of the solvent was recovered. The built in recovery of this novel solvent enables for economically competitive and sustainable processes.