Acid-Catalyzed Synthesis of Six-Membered Cyclic Acetal from Condensation of Benzaldehyde and Glycerol

Abstract

Based on the condensation reaction of glycerol with benzaldehyde, the effects of acid catalysts (p-toluenesulfonic acid(PTSA), phosphotungstic acid(PWA), KHSO4 and FeCl3, respectively) on the yield of the condensation products and the mass ratio of 5-hydroxyl-2-phenyl-1,3-dioxane(1) to 4-hydroxymethyl-2-phenyl-1,3-dioxolane(2) were investigated. Comparison tests indicated that under the conditions of cyclohexane as water entrainer and n(benzalhydehyde)∶n(glycerol)=2∶3, KHSO4 gave the best yield(96.8%) of condensation products(compound 1+2) and PTSA yielded the highest proportion(m(1)∶m(2)=48.6∶51.4) of compound 1 in condensation products(compound 1+2. At room temperature, PTSA, PWA, KHSO4 and FeCl3 all can, but at -20 ℃, only PTSA can catalyze the transformation of compound2 to compound 1. Cis-5-hydroxyl-2-phenyl-1,3-dioxane(1a) was isolated by the catalytic transformation of compound 2 with PTSA at -20 ℃ and crystallized from a mixture of V(benzene)∶V(ligroin)=40∶60. Compound 1a was obtained by recycling the catalytic transformation of compound 2 in the mother liquor three times in a accumulative yield of 91.1%.