Catalytic synthesis of acetals and ketals with H3PW12O40PAn

A new environmental friendly catalyst H3PW12O40/PAn was prepared and identified by means of FT-IR, XRD, and TG/DTA. The optimum conditions have been found; that is, the mass ratio of PAn to H3PW12O40 is 1:1.5, the volume of methanol is 20 mL, and the reflux reaction time is 3 h. The structural identity of Keggin units is preserved after the incorporation into polyaniline matrix. Catalytic activities of H3PW12O40/PAn in synthesizing 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane,2,4-dirnethyl-2-ethoxycarbonylmethyl-1,3-dioxolane, cyclohexanone ethylene ketal, cyclohexanone 1,2-propanediol ketal, butanone ethylene ketal, butanone 1,2-propanediol ketal, 2-phenyl-1,3-dioxolane, 4-methyl-2-phenyl-1,3-dioxolane, 2-propyl-1,3-dioxolane, and 4-methyl-2-propyl-1,3-dioxolane were reported. It has been demonstrated that H3PW12O40/PAn is an excellent catalyst. Various factors concerned in these reactions were investigated. The optimum conditions are as follows: the molar ratio of aldehyde/ketone to glycol (r) is 1:1.5, the mass ratio of the catalyst used to the reactants is 0.6%, and the reaction time is 1.0 h. Under these conditions, the yield is as follows: 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane, 69.0%; 2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane, 79.5%; cyclohexanone ethylene ketal, 78.9%; cyclohexanone 1,2-propanediol ketal, 85.3%; butanone ethylene ketal, 56.9%; butanone 1,2-propanediol ketal, 78.1%; 2-phenyl-1,3-dioxolane, 76.3%; 4-methyl-2-phenyl-1,3-dioxolane, 94.2%; 2-propyl-1,3-dioxolane, 70.7%; and 4-methyl-2-propyl-1,3-dioxolane, 79.2%.