Synthesis of 4-Methyl-2-Isopropyl- 1,3 -Dioxolane by TiSiW12O40/ TiO2 as Catalyst

Acetals and ketals are a kind of the important compounds and used to protect carbonyl,middle material of the organic synthesis. What's more, they are a sort of the widely use flavor substance. 4-Methyl-2-isopropyl-1,3-dioxolane has fresh fruit odor and apple note. It is used to producing many sorts of essence. And the conventional method to synthesize 4-methyl-2-isopropyl-1,3-dioxolane makes use of sulfuric acid as catalyst in factories. But it causes many problems, such as the erosion of production equipment, difficulty after-treatment, low quality of the products, etc. HPA and its salts shows excellent catalytic activity to the esterification and have recently attracted much attention as catalysts for various industrial processes, because their acidic and redox properties can be controlled at atomic/molecular levels. Misono, Pope [1], and Wang [2]have reviewed the homogeneous catalysis and fine organic synthesis catalyzed by heteropoly compounds. However, there is no report on the synthesis of 4-methyl-2-isopropyl-1,3-dioxolane catalyzed by TiSiW12O40/TiO2. TiSiW12O40/TiO2 was prepared according to reference [3] and identified by means of IR and XRD. The reaction was carried out in a three-neck flask equipped with a stirrer, a reflux condenser, and a thermometer. A certain amounts of isobutyraldehyde,1,2-propanediol and the catalyst was heated to boiling and refluxed until no water flowed off. The purified product was analyzed by IR spectra and 1HNMR.In this paper, we report 4-methyl-2-isopropyl-1,3-dioxolane was synthesized from isobutyraldehyde and 1,2-propanediol in the presence of TiSiW12O40/TiO2. The factors influencing the yield of product and the optimum reaction conditions were discussed. The optimum conditions are molar ratio of isobutyraldehyde to 1,2-propanediol was 1:1.5, the quantity of catalyst was equal to 0.5% feed stock, and the reaction time was 1.0 h. TiSiW12O40/TiO2 was an excellent catalyst to synthesize 4-methyl-2-isopropyl-1,3-dioxolane and the yield can be up to 92.1%. IR spectra of 4-methyl-2-isopropyl- 1,3-dioxolane shows peaks at 1191,1100,1022,950 cm-1; 1HNMR (δH, ppm):4.65-4.67 (d, 1H, CH), 4.02-4.20 (m, 1H, CH), 3.81-3.92 (d, 1H, CH), 3.35-3.43 (t, 1H, CH),1.61～1.85 (m, 1H, CH), 1.14-1.29 (d, 3H, CH3), 0.96 (m, 6H, CH3); nD20=1.4135; b.p. 127-130 ℃.And we found that the catalyst can be utilized repeatedly, moreover, the catalytic activities of the catalyst are almost unchanged after it has been used five times. From the above results and discussion, we can see that the synthesis of 4-methyl-2-isopropyl-1,3-dioxolane catalyzed by TiSiW12O40/TiO2 instead of sulfuric acid has a great prospect of application.