酸催化甘油与苯甲醛缩合制备六员环缩醛

比较了对甲苯磺酸（PTSA）、磷钨酸（PWA）、KHSO₄和FeCl₃催化对甘油与苯甲醛的缩合反应收率，及对产物中六元环缩醛5-羟基-2-苯基-1,3-二氧六环(1)与五元环缩醛4-羟甲基-2-苯基-1,3-二氧五环(2)比例的影响。 当以环己烷为带水剂及苯甲醛与甘油的摩尔比为2∶3的情况下，KHSO4为催化剂的缩合产物（1+2）收率较高，为96.8%；PTSA催化的缩合产物中，化合物1的比例最高(m(1)∶m(2)=48.6∶51.4)。 室温下PTSA、PWA、KHSO₄和FeCl₃均可催化化合物2向化合物1的转化。 在-20 ℃下，只有PTSA能催化化合物2向化合物1的转化。 在-20 ℃，PTSA催化化合物STHZ]2转化成化合物1a,并以晶体形式从苯（40%）-石油醚（60%）中析出。 母液循环转化3次后，化合物1a的累计收率可达91.1%。

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

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%.