Ionic liquids as recyclable reaction media for the tetrahydropyranylation of alcohols

摘要

A comparative study of the catalysed tetrahydropyranylation of 1-phenylethanol by p-toluenesulphonic acid (TsOH),pyridinium p-toluenesulphonate (PPTS) and triphenylphosphine hydrobromide (TTP.HBr) usign 3,4-dihydro-2H-pyran in dichloromethane or in the ionic liquids 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF_4]) or 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF_6]) showed that the reaction occurs readily in [bmim][PF_6] for PPTS or TPP.HBr by a non-reversible process.These reaction media were recycled on 22 occasions without loss of activity and their scope of application to other alcohols was also studied.