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

Abstract

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 β-pinene to α-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.

Butadiene sulfone as ‘volatile’, recyclable dipolar, aprotic solvent for conducting substitution and cycloaddition reactions

“…A control reaction was conducted: TsCN was added to DMSO at 50 °C; no benzyl azide was present. After 4 days most of the TsCN disappeared with the formation of a major product, and 1 H NMR analysis of the control reaction at 2 and 4 days showed that the major product is a salt of p-toluenesulfonic acid (see 1 H NMR spectra in Additional file 1: Fig. S1).…”

“…Unfortunately, the isolation of reaction products and the recyclability of the solvent is often times difficult as well as economically expensive. Recently a couple of sulfolene solvents have been proposed as possible recyclable substitutes for DMSO [1][2][3][4][5][6]. Piperylene sulfone is a liquid at room temperature and butadiene sulfone is a liquid at 64 °C.…”

Piperylene Sulfone: A Smart Solvent

“…Otimizadas as condições reacionais, 11 alcoóis primários benzílicos e alílicos foram testados e mostraram bons resultados frente à oxidação (entre 84 e 98 % de rendimento e conversão por CG de 88 a 100 %) ( Tabela 3) O terceiro trabalho trata do emprego da piperileno sulfona (1) como solvente na hidrólise catalítica de β-pineno (10) a αterpineol (11, Esquema 3). 21 Esquema 2. Oxidação do álcool 4-metoxibenzílico com catalisador de cobre, na presença de acetamido-TEMPO e piperileno sulfona (1) como solvente (adaptado da ref.…”

Switchable butadiene sulfone pretreatment of Miscanthus in the presence of water

“…65 °C) 20 with the unique ability to "switch" from solvent to gaseous 1,3-butadiene and sulfur dioxide in a reversible reaction 21,22 that favors BS below 100 °C and the gases above 100 °C. 23 In the presence of water, sulfur dioxide forms in situ sulfurous acid 23 which can act as a catalyst in deconstructing lignocellulosic biomass, 19 and as such, it can break ester bonds connecting hemicellulose and lignin, with the delocalization of the amorphous structure of hemicellulose and subsequent acid hydrolysis. 7 The involvement of BS in lignin solubilization, during or after xylan hydrolysis, is discussed in this study (Fig.…”

“…The facile and scalable recyclability of BS is an advantage over traditional acid/alkali pretreatments and novel ionic-liquid based pretreatments. The former would involve neutralization and further processing to remove contaminant salt by-products 23,25 and the latter require difficult recycling processes not yet at large scale operations. 26 Another advantage of BSW pretreatment is the inexpensive commercial availability of BS, compared for instance, to ionic liquids, which are 5-20 times more expensive than conventional solvents at the laboratory scale 27 and require in many cases the addition of an acid-catalyst.…”