Study On Synthesis Of Pseudoionone With Solid Base Catalysts

Pseudo-ionone is the key intermediate for synthesis of some chemical andpharmaceutical products such as ionone, vitamin A and E. In the present, ionone is obtainedby acid-catalyzed cyclization of pseudo-ionone, which is prepared by the condensation ofcitral with acetone catalyzed by alkaline catalyst at home and abroad.The alkaline catalytic systems are used in the synthesis of the pseudo-ionone, such as theliquid base-catalytic system, including basic aqueous systems, basic alcohol system, and thebasic phase-transfer catalysis; the solid base catalyst systems, including use of NaOH/Ba（OH）2as catalyst, metal hydroxides, metal oxides and composite solid hydroxide as a catalyst,an anion exchange resin, basic carrier as a catalyst, and so on.In this paper, the pseudo-ionone preparation from the condensation of citral with acetonecatalyzed by D201, D261-type macrospore strong base Resins and solid powder LiOH· H₂Oas a solid base catalyst was researched under condition of the ultrasound radiation or oscillator.The related factors on the yield or selectivity of pseudo-ionone and the conversion of citralwere examined such as reaction time, the amount of catalyst, reaction temperature, the molarratio of central to acetone, catalyst recovery efficiency, etc.The results showed that the two types of macro porous strong base resins D201andD261had a strong catalytic performance. Under optimal reaction conditions, the yield ofpseudo-ionone catalyzed by D201was up to95.77%; The conversion of citral was98.65%and the selectivity of the pseudo-ionone was95.03%catalyzed by D206. Under the sameconditions, the catalytic performance of D206was slightly better than the D201, but therecycled use of the two catalysts were both unsatisfactory.Under the optimal conditions, the conversion of citral could reach to98.01%and theselectivity of pseudo-iononewas98.30%by the condensation of central with acetonecatalyzed by Solid powder LiOH· H₂O.The catalyst can be conveniently recovered forrecycled use multiple times. This method has advantages of high conversion, high selectivity,short reaction time, no environmental pollution, simple work-up procedure, and catalyst canbe conveniently recovered for recycling. And it is accorded with the production of greentechnology. It is better than the other reported methods for the synthesis of pseudo-ionone. Therefore, LiOH· H₂O is the ideal catalyst for synthesis of pseudo-ionone by aldolcondensation of citral and acetone. Maybe, this method can also be applied to the other aldolcondensation reaction.