Research On Synthesis Of β-Carotene And Canthaxanthin

Processes for P-carotene and canthaxanthin synthesis were investigated. Intermediates and target products were analyzed by melting point, refractive index,GC,GC/MS,HPLC,IR,'H-NMR and 13C-NMR to confirm their structures.1 -(2,6,6-Trimethyl-1 -cyclohexenyl)-3-methyl-1 -buten-4-al(C 14-aldehyde) was obtained from fS-ionone by cyclic oxidation -. cyclic opening and then by rearrangement. Wittig-Horner reaction was conducted by reacting C₁4-aldehyde with tetraethyl methylenediphosphonate(obtained by Arbuzow reaction) to get 3-methyl-5-(2,6,6-trimethyl-1 -cyclo-hexenyl-1 yl)-1,3-diethylpenta dienephosphonate(unrearr-angement C₁5-phosphonate). Pressure synthesis process for trimethylsulfbnium bromide was applied. Liquified methyl bromide and dimethyl sulfide react under pressure and less volatile materials loss to get a cleaner surroundings. C₁4-Aldehyde synthesis is a carbon-saving process and consumes methyl bromide.Progress was made in C₅-aldehyde synthesis.Isoprene and hypochlorous acid reacted to prepare chlorhydrin, which was coverted to 4-acetyloxy-2-methyl-2-butenal(C5-aldehyde) by esterification and Kornblum catalytic oxidation. Chlorhydrin synthesis process produces no solid byproducts by using CO₂ instead of organic acid. Cation exchange resins loaded perchloric acid are applied as catalysts and easy to be recycled. New composite catalyst is used in Kornblum oxidation to enhance Cs-aldehyde yield.Acetal reaction and ester exchange were applied to acquire 3-(5,5,-dimethyl-l,3-dioxan-2-yl)-2-buten-l-ol from Cs-aldehyde.The obtained alcohol was transformed to 3-(5,5-dimethyl-l,3-dioxan-2-yl)-2-butenal via 2,2,6,6-tetramethyl-l-piperidinyloxy free radical(TEMPO) catalytic oxidation cooperated with Cu₂Cl₂.Meanwhile,chlorination was put forward to get 2-(3-chloro-l-methyl-l-propenyl)-5,5-dimethyl-l,3-dioxane by using the obtained alcohol with SOCl₂.2,7-Dimethyl-2,4,6-octatriene-l,8-dial was obtained in 78.7% yield by "one pot method"from 3-(5,5-dimethyl-l,3-dioxan-2-yl)-2-butenal,2-(3-chloro-1 -methyl-1 -propenyl)-5,5 -dimethyl-1,3 -dioxane and triethylphosphite. Mechanism for TEMPO catalytic oxidation cooperated with Cu₂Cl₂ was proposed.Cu( I) and enol form enol complex.TEMPO O₂ and proton make odd electronic oxidant nitrosium ion. Nitrosium ion oxidate enol complex obtains target aldehyde and release Cu( I) and hydroxylamine. Hydroxylamine combines nitrosium ion to form TEMPO. An equilibrium of Cu( I ) consuming nitrosium ion also exists in oxidation system. Nitrosium ion synthesis is the control step.(3-Carotene was prepared by Wittig-Horner reaction which applied unrearrangement C₁5-phosphonate and 2,7-dimethyl-2,4,6-octatriene-l,8-dial. This Process overleaps the rearrangement step enhance a yield of 10.4%.New P-carotene catalytic oxidation process was proposed to make canthaxanthin which protect P-carotene and canthaxanthin maintain their properties by CO₂. Recrystallization process was applied to purify P-carotene and canthaxanthin. Synthesis of C₁4-aldehydeProper conditions for trimethylsulfonium bromide synthesis: methyl bromide/dimethyl sulfide=1.45(mol/rnol),20°C,0.6Mpa, 8h,trimethylsulfonium bromide was obtained in 95.5% in acetone.Cyclic oxidation process: NaOH/trimethylsulfoniumbromide/p-ionone=1.7:1.4 :l(mol/mol),50,9h,getting l-(2,6,6-trimethyl-l- cyclohexenyl )-3-SR-methyl-3,4-epoxy-l-butene(epoxy compound) in 83.7% yield.Methyl bromide reacted with magnesium and got magnesium bromide as catalyst.Cyclic opening of epoxy compound in -10 THF obtained 1-(2,6,6-trimethyl-l-cyclohexenyl)-3 -methyl- l-buten-4-al in 97% yield.The aquired aldehyde was catalyzed by KOH and rearranged in methanol at room temperature to get C₁4-aldehyde by 95% yield. Unrearrangement C₁5-phosphonate synthesisArbuzow reaction process: triethyl phosphate/dibromomethane=3(mol/mol),150 , tetraethyl methylenediphosphonate was aquired in 73% yield.Appropriate Wittig-Horner reaction conditions:sodium hydride/tetraethylmethyl enediphosphonate/C₁4-aldehyde=0.9:1.25/l(mol/mol),20,2h,ThusC₁5-phos-phonate was got in toluen...