Switchable Solvents for in-Situ Acid-Catalyzed Hydrolysis of β-Pinene

Conventional acid-catalyzed reactions use homogeneous catalysts that generate large amounts of waste due to neutralization processes. We can eliminate such waste with the use of switchable solvents such as butadiene sulfone and piperylene sulfone, which can act as reaction media and generate reversible, in-situ acid catalysts. These solvents enable separation through use of a thermal switch, which shifts the equilibrium from the nonvolatile, polar aprotic solvent to highly volatile products. This equilibrium generates sulfurous acid through the addition of water, enabling acid-catalyzed reactions and easy separation due to the unstable nature of the acid at reversal temperatures. In this work, we use these switchable solvents to complete the hydrolysis of beta-pinene to alpha-terpineol. We show a kinetic study of the hydrolysis reaction, illustrating high activity and selectivity in the novel reaction media. Further, we illustrate recycle of the solvent and catalyst five times without loss in activity or need for neutralization processes.