Tetraalkylammonium Ionic Liquids as Dual Solvents–Catalysts for Direct Synthesis of Sugar Fatty Acid Esters

Abstract

Abstract As nonionic surfactants derived from naturally renewable resources such as sugars and fatty acids, sugar fatty acid esters have been widely utilized in food, cosmetic and pharmaceutical industries. Our present study has demonstrated that the inexpensive and halogen‐free tetraalkylammonium salts (e.g., [Bu 4 N][Ac], [Et 4 N][Ac] and [Me 4 N][Ac]) can act as dual solvents–catalysts for regioselective acylation to produce glucose laurate. This non‐enzymatic synthesis can proceed under mild conditions with high specificity, and the conversions obtained were superior to that when an enzyme catalyst (lipase, EC 3.1.1.3) was added. A higher yield was obtained in the ammonium salt with a longer alkyl chain on the cation, while no product was obtained in [Bu 4 N][HSO 4 ] and [Bu 4 P][Ac]. A reaction mechanism has been proposed, which is supported by phase‐transfer catalysis and law of matching water affinity.