Study On The Synthesis Of Piperonyl Butoxide

Piperonyl butoxide is the only highly effective, nontoxic and extensive synergist approved by FAO (Food and Agriculture Organization of the United Nations). It is used in a wide variety of pesticides, such as agricultural pesticides for food and nonfood crops, pesticides for indoor home use such as dust, sprays, and foggers, pesticides for stored products, pesticides for gardens, lawns, and decorative plants, pesticides for human clothing, bedding, and mattresses, and so on.Synthesis of piperonyl butoxide was summarized in this thesis. A new route was proposed, in which piperonyl butoxide was synthesized via Friedel-Crafts acylation, Wolff-Kishner-Huangminglong reduction, Blanc chloromethylation and Willamson ethrification, with 1,3-Benzodioxole as the starting material. The new proposal is advanced in many aspects. The use of 1,3-Benzodioxole cannot only cut the cost, but also avoid destroying the plants which was used for extracting safrole. In the Friedel-Crafts acylation step, the used of propionyl chloride is atom economic. Besides, the highly selectivity catalyst, zinc chloride, results in less by-products and can be recycled. Compared to the previous Clemmensen reduction, the Wolff-Kishner-Huangminglong method is less toxic and carried out under milder conditions. Quantum chemical mechanisms of the Blanc chloromethylation and Willamson ethrification were investigated. The induction of phosphorus trichloride in Blanc chloromethylation increased the yield of piperonyl butoxide, and the reuse of inorganic phase decreased the exhaustion of wast water.The reaction conditions of each step are as follows:1. Friedel-Crafts acylation of 1,3-Benzodioxole. Propionyl chloride reacted with 1,3-Benzodioxole in dichloroethane at 0～5℃for 24 h catalyzed by Zinc chloride under the conditions:molar ratio (n(1,3-Benzodioxole):n(propionyl chloride):n(Zinc chloride)=1:1.2:1.5).5-propionyl-1,3-benzodioxole was obtained with yield of 91.6%.2. Wolff-Kishner-Huangminglong reduction of 5-propionyl-1,3-benzodioxole. Hydrazine hydrate (85 wt%conc.) reacting with 5-propionyl-1,3-benzodioxole under reflux in toluene for 3-4 h resulted in hydrazone. Postassium hydroxide and the phase-transfer catalyst. PEG-400 (3-5 wt%), were added after removing the water by azeotropying with toluene, subsequent 12 h reaction under reflux gave 90.6% yield of dihydrosafrol. The optimized reaction conditions are:molar ratio (n(5-propionyl-1,3-benzodioxole):n(hydrazine):n(postassmm hydroxide)=1:2:2).3. Blanc chloromethylation and Willamson etherification. Dihydrosafrol reacted with paraformaldehyde and hydrochloric acid (38wt% conc.) in cyclohexane at 70℃for 6 h while phosphorus trichloride was added dropwise continuously. The organic phase was then separated and nutralized. Without further purification, add sodium hydroxide and diethylene glycol monobutyl ether to the organic phase under reflux and stir for 5.5 h. Meanwhile, the water was removed by azeotropying with cyclohexane. Piperonyl butoxide was obtained by vacuum distillation, with yield of 91.8% for the two steps. The optimized reaction conditions are:molar ratio (n(Dihydrosafrol):n(formaldehyde):n(hydrochloric acid)=1:2:2), molar ratio (n(Dihydrosafrol):n(sodium hydroxide):n(diethylene glycol monobutyl ether)=1:1.5:1.3).The final product piperonyl butoxide was prepared in 76.2% yield with a purity of 97.8% under the conditions above, and the structure of each product is confirmed by 1H-NMR,13C-NMR, MS and so on.The new method developed in this work has obvious advantages and it is suitable for scale-up production.