Activation of 1,3-dioxolane by a protic ionic liquid in aqueous media: a green strategy for the selective hydrolytic cleavage of acetals and ketals

Abstract

A convenient method for the deprotection of acetals and ketals was achieved using an imidazolium based protic ionic liquid as a catalyst in aqueous medium via the dual activation of dioxolane. The protocol is highly efficient towards the deprotection of acyclic and cyclic acetals, ketals, benzylidene acetals and tetrahydropyranyl (THP) ethers, giving excellent yields. Functional groups such as tert-butyl ester, tert-butyl dimethyl silyl (TBDMS), N-tert-butyloxycarbonyl (N-Boc), and double bond, mesyl, nitro, and glycosidic linkage were tolerated under the benign reaction conditions. Selective deprotection of the 5,6-isopropylidene moiety in 1,2:5,6-di-O-isopropylidene hexose and 3,5-cyclohexylidene moiety in pentose derivatives proceeded smoothly without affecting the 1,2-protected group. The attractive features of this new protocol are the use of mild reaction conditions, tolerance of a wide range of functional groups, use of relatively non-toxic solvent systems and recyclability of the ionic liquid catalyst.