2,3-二甲氧基-5-甲基-1,4-苯醌的合成

以3,4,5-三甲氧基甲苯(TMT)为原料,先由V ilsm e ier-Haack反应合成6-甲基-2,3,4-三甲氧基苯甲醛,然后在对甲基苯磺酸催化下经Dak in反应将其氧化为6-甲基-2,3,4-三甲氧基苯酚,最后用重铬酸钠催化氧化合成了辅酶Q0,过程总收率达到72.3%。经正交实验得V ilsm e ier-Haack反应的最佳工艺为:n(TMT)∶n(POC l3)∶n(DMF)=1∶1.8∶2.2,反应温度70℃,反应时间7 h。在此工艺条件下,此步反应收率可达93.2%,w(6-甲基-2,3,4-三甲氧基苯甲醛)=98.5%;在Dakin反应中,以w(H2O2)=30%为氧化剂,30℃为最佳反应温度,反应时间1.5 h。

Synthesis of 2,3-Dimethoxy-5-methyl-1,4-benzoquinone

Coenzyme Q_0(2,3-dimethoxy-5-methyl-1,4-benzoquinone) was synthesized through three-step process employing 3,4,5-trimethoxytoluene(TMT) as the starting material.The first step,involving Vilsmeier-Haack reaction,gave 6-methyl-2,3,4-trimethoxybenzaldehyde.The next step,involving Dakin Reaction with p-toluensulfonic acid as the catalyst,gave 6-methyl-2,3,4-trimethoxypenol.In the last step,Coenzyme Q_0 was prepared through catalytic oxidation with sodium dichromate as the oxidant.The overall yield reached 72.3%(based on TMT).The most favorite technological conditions of Vilsmeier-Haack Reaction are:n(TMT)∶n(POCl_3)∶n(DMF)=1∶1.8∶2.2,70 ℃ and 7 h.Under the optimum conditions,a yield of 93.2% with the purity of 98.5% in Vilsmeier-Haack reaction was obtained.For Dakin reaction,reaction temperature is the major effective factor,and the optimal reaction temperature and reaction time are 30 ℃ and 1.5 h respectively.