2,3-戊二酮的合成

乙醛和丙醛经3-乙基-4-甲基-5-(2-羟乙基)-1,3-噻唑溴盐催化交叉偶联反应生成以C5偶姻为主的偶姻混合物,偶姻混合物再经H2O2间接氧化、分离制备了2,3-戊二酮。优化的偶联反应条件是:m(乙醛)∶m(丙醛)∶m(催化剂)∶m(Na2CO3)=110∶90∶2∶1;反应温度125℃;压力为1MPa。乙醛和丙醛转化率分别达到94%和95%,C5偶姻产率为48.8%,偶姻总产率为90%。混合偶姻在浓H2SO4存在下,用质量分数30%H2O2/FeSO4.7H2O氧化,m(FeSO4.7H2O)∶m(浓H2SO4)∶m(H2O)∶m(偶姻)∶m(H2O2)=11∶2∶4∶2∶3,2,3-戊二酮相对于偶姻的总产率为44%,邻二酮总产率为84%。经常压分馏,可以分别得到质量分数≥98%的2,3-戊二酮、丁二酮和3,4-己二酮产品。铁离子氧化剂重复使用,邻二酮化合物收率没有明显下降。

Synthesis of 2,3-Pentanedione

The acyloin mixture,which mainly consist of C5 acyloins,was synthesized from acetaldehyde and propional by the cross-condensation under the catalysis of 3-ethyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazolium bromine.2,3-Pentanedione was obtained via the oxidation of the mixture indirectly by H2O2 and separation.The optimized cross-condensation reaction conditions were:m(acetaldehyde):m(propional):m(catalyst):m(sodium carbonate)=110:90:2:1;reaction temperature 125 ℃;the pressure 1 MPa.The conversions of acetaldehyde and propional were 94% and 95% respectively.The yield of C5 acyloins was 48.8%,and the total condensation products amount to 90%.In the presence of the concentrated sulfuric acid,acyloin mixtures were oxidized by 30%H2O2/FeSO4·7H2O,m(FeSO4·7H2O):m(sulfuric acid):m(water):m(acyloins):m(H2O2)=11:2:4:2:3.The yield of 2,3-pentanedione on the gross weight of acyloins was 44%.The total yields of vic-diketones amount to 84%.2,3-Pentanedione,2,3-butanedione and 3,4-hexanedione can be obtained with purities more than 98% by atmospheric distillation.The iron salt could be reused without obviously decreasing the yields of vic-diketones.