Acetylation of β-cyclodextrin in ionic liquid green solvent

The ionic liquid (IL), 1-butyl-3-methylimidzolium bromide ([C4mim]Br), synthesized under supercritical CO2, was developed as a green solvent for the dissolution, regeneration and acetylation of β-cyclodextrin (β-CD). The dissolution of β-CD in [C4mim]Br of 25 wt% could be reached at 25 °C. The acetylation of β-CD was carried out under acetic anhydride in [C4mim]Br in the absence of catalyst. β-CD acetates with different degrees of substitution of 0.07–1.14 were obtained directly under the homogeneous reaction conditions. The reaction medium of IL applied can be easily recycled and reused after the synthesis of β-CD acetate. The effects of reaction time, temperature, and acetic anhydride/AGU on the acetylation of β-CD were investigated. The acetylated β-CD samples were characterized by NMR, FT-IR, and X-ray diffraction (XRD) spectroscopy. It is the first time that we have demonstrated that ILs can be used as an environmentally friendly solvent for the acetylation of β-CD, which will open a new route to acetylation of β-CD under green solvent without catalyst.