Synthesis of dioxanes via Prins reaction catalyzed by acyclic acidic ionic liquids

Some recyclable acyclic SO3H-functionalized ionic liquids have been used as environmentally benign catalysts for the synthesis of dioxanes by Prins reaction. The products could simply be separated from the catalysts by decantation. After separation from the reaction mixture the catalysts could be recycled and reused for several times without a noticeable decrease in the catalytic activity.