Synthesis of 2,4-diisopropyl-5,5-dimethyl-1,3-dioxane catalyzed by Br nsted acidic ionic liquids

The acetalization reactions of isobutyraldehyde with 2,2,4-trimethyl-1,3-pentanediol (TMPD) for the synthesis of 2,4-diisopropyl-5,5-dimethyl-1,3-dioxane were carried out under mild reaction conditions using four water-stable Br nsted-acidic task-specific ionic liquids ([HMIM]BF4, —SO3H functionalized acidic ionic liquid, —COOH functionalized acidic ionic liquid, [NMP][HSO4]) as environmentally benign catalysts for the first time. The process is highly effective and very selective. The —COOH functionalized Br nsted acidic ionic liquid with the two acid sites (IL-3) exhibited the most excellent catalytic performance under mild reaction conditions. The —COOH functionalized Br nsted acidic ionic liquid could be conveniently separated from the product and easily recycled in subsequent runs.