| Retinol acetate is the essential substance for the body growth and development,reproduction and visual system.It can also adjust the growth and health of the epidermic histiocyte to make crude and aging skin surface thin,which can promote cell metabolism and dispel wrinkles.A lack of vitamin A can cause poor appetite,dry skin and nyctalopia.Furthermore,retinol acetate is also widely used as feed additives.Dialkyl 3-methyl-5,(2,6,6-trimethylcyclohex-l-enyl)-2,4-pentadienyl-l-phosph-onate(referred to as 2,4-diene-C15-phosphonate)is the key intermediate for the synthesis of retinol acetate via C15+C5 synthetic route characterized by Wittig-Horner condensation.The reported method for the synthesis of 2,4-diene-C15-phosphonate is based on:a Darzens condensation between β-ionone and methyl chloroacetate leading to C14-aldehyde,followed by a Wittig-Homer condensation between the above C14-aldehyde and methylenebisphosphonic acid tetraethyl ester producing 1,3-diene-C15-phosphonate,and then 1,3-diene-C15-phosphonate rearranged to 2,4-diene-C15-phosphonate.But this synthetic route is too long and the phosphorus wastewater is too much.So it is necessary to develop a new facile,efficient and environmentally friendly methodology for the synthesis of 2,4-diene-C15-phosphonate.A novel route for the synthesis of 2,4-diene-C15-phosphonate is described in this paper.Only one step between β-ionone and tetraethyl ethylenebisphosphonate via Wittig-Homer condensation is needed to obtain the target product 2,4-diene-C15-phosphonate.Furthermore,an efficient method for the handling of the by-product phosphorus wastewater is also developed.The wastewater including sodium diethyl phosphate undergoes neutralization with acid,pyrolysis at high temperature and rectification under vacuum,then high content of triethyl phosphate can be obtained in good yield.The key process of this technic is described as follows:Firstly,sodium dietyl phosphite was prepared by reaction of dietyl phosphite and sodium ethoxide.It was then reacted with ethylene dibromide with the molar ratio of 4.5 at 30 ℃ in 72 hrs to obtain tetraethylethylenebisphosphonate,in which the content of alcohol should be no more than 1.5%.The intermediate tetra-ethylethylenebisphosphonate can be purified by distillation under 120～125 ℃/133.3Pa with the content of 96.1%and the overall yield of 72.0%.The structure was confirmed by 1HNMR;13CNMR and GC-MS.Then,the target product 2,4-diene-C15-phosphonate was synthesized via the condensation of β-ionone and tetraethylethylenebisphosphonate with the molar ratio of 1:1.05 at 40 ℃ in 6 hrs catalyzed by a base in aproticsolvent.The yield is 58.0%with the content of more than 92.3%according to GC analysis.The structure was confirmed by 1HNMR,13CNMR and IR.Furthermore,a facile and economic method to handle the phosphorus wastewater has been developed.The wastewater including sodium diethyl phosphate undergoes neutralization by acid,pyrolysis at high temperature and rectification under vacuum,then high content of triethyl phosphate was obtained.This method has been applied in the industrial production.Also,the recovery of the phosphorus resource in the wastewater from the Wittig-Horner condensation can be resolved via the following process.Sodium diethyl phosphate was reacted with concentrated sulfuric acid with the molar ratio of 1:1.05 at 50℃ to obtain diethyl phosphate,in which the separation of the organic layer should be at 30 ℃.Then,the pyrolysis was carried out at 180～200 ℃ under vacuum,and the fraction of crude triethyl phosphate was collected under 100～110 ℃with the content of more than 99%according to GC,moisture content of 0.12%,acid value of 1.1mgNaOH/g and the yield of 85%.The structure was compared with the standard sample and confirmed with GC-MS.The recovery rate of the phosphorus is 83%,and the overall COD emission has a decrease of 98.4%.This method has been carried out in pilot scale and will be applied in the industrial scale. |
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