Study On The Novel Process For Preparation Of Vitamin A By Witty Method

Vitamin A is one of the essential Vitamin in human and animal body. Besides using for the treatment moon blindness, conjunctiva and cornea dry, it can also be used as food nutrition enhancer and animal feed additive. Recently, the results of the research works indicate that vitamin A can cure various cancers. In 1947 Switzerland scientist Isler proposed the scheme of synthesis of Vitamin A acetate, then Roche set up industrial prosess in 1948. Vitamin A was manufactured by Shanghai No.6 Pharmaceutical Factory and Northeast Pharmaceutical Factory in 1964 in China firstly.Based on the retrieval and review of the bibliographer, the original process for preparation of Vitamin A in Zhejiang Xinchang Chemical co., Ltd was evaluated. The novel process for preparation of Vitamin A starting fromβ-ionone by hydrogenation, preparation of phosphine salt, Wittig condensation and isomerization was proposed and studied. The factors which affect the yield and the quality of the product such as the ratio of raw material, reaction temperature, pressure, reaction time were studied experimentally. The optimal parameters of the novel process were selected. The devices of the process were evaluated systematically according to the results of the experiment.Ethynylation and optimizing reaction condition for the ethynyl-β-ionol fromβ-ionone was studied and decided as follows. The best solvent is ether for the C₂HLi·NH₃ process. The best metal is lithium. The best acetylene to ammonia ratio(mol:mol) is 25:65. The optimizing reaction temperature is 0℃and the yield was 98.8%.Synthesis of vinyl-β-ionol via hydrogenation was studied from ethynyl-β-ionol. The conversion and selectivity were optimized. The favourable compositive catalyst for the hydrogenation which had a certain ratio was evaluated. The conversion and selectivity were 98% and the yield was 96%.Phosphine salt was prepared and optimizing reaction conditions was selected as follows: the best ratio 1 : 1.06 : 1.3 : 0.6(vinyl-β-ionol:Ph₃P:HBr:primidine), the reaction temperature 50℃. The yield was 95%.Vitamin A acetate process was discussed. The best base was CH₃ONa which was 1.4 times to phosphine salt in ethanol. The best isomerization solvent was n-hexane. The Wittig reaction yield was 91.5% (including cis-and trans-) and 85% trans-vitamin A acetate was obtained by isomerization. The purity of trans-vitamin A acetate amounted to 97.8% after crystalization. The total yield was about 75% based on C₅.It provided the theoretical basis for the industrial production of trans-vitamin A.