5 最后一段翻译
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5.2 合成过程中的影响因素及方法比较
实验中第一步用新制备的PCC氧化效果较好,用琼斯试剂氧化也可以得到4-
烯-3,6-二酮,但产率低副产物多。第二步选择性还原中,经过NiCl2·6H2O的催
化后,得到的产物为混合物,在此不必分离,再经第三步用琼斯试剂氧化后,得
到化合物(4)。在第四步肟化反应中,底物与NH2O·HCl物质的量之比为1︰1,
为了防止化合物活性过大,将温度设定在45℃左右,为了能够使体系中生成选择
性位阻较小的3位肟基,在投料时遵循少量多次的原则,避免生成两个肟基。在
第五步生成4-氮杂-A-homo-胆甾-3,6-二酮的贝克曼重排反应中,无水条件和反应
时间的控制是贝克曼重排反应的关键。SOCl2极易水解,若体系中有水存在,
SOCl2立即与水反应生成HCl和SO2,将降低SOCl2的催化能力及增加副产物。若
反应时间过长,也会生成很多副产物。得到的产物中有异构体,较难分开,采用
梯度法过柱效果较好。
5.2 The influences and method comparison of synthesis
The oxidation effect of freshly prepared PPC was good in the first step of the
experiment. The cholest-4-en-3,6-dione was obtained by oxidation with Jones’ reagent,
but was with more by-product and in low yield. The products were mixture witch
were obtained by selective reduction under the catalysis of NiCl2·6H2O in the second
step, the mixture was without separation, then the mixture was oxidated with Jones’
reagent to give compound 4 in the third step. In the fourth step oximation reaction, the
mole ratio of substrate and NH2O·HCl was 1:1, the reaction temperature was about
45 ℃ to preventing the reactant from being more active, the low steric hindrance
3-oxime was obtained by frequent and small amounts feeding and di-oxime was
avoided being generated. In the fifth step, anhydrous conditions and control reaction
time was the key component of the Beckman rearrangement reaction of the synthesis of
4-aza-A-homcholest-3,6-dione. SOCl2 is easy to be hydrolyzed to give HCl and SO2
with the presence of water, it will reduce the catalytic ability of SOCl2 and generate
more by-product. More by-products were prepared when the reaction was long. There
were isomers in the products, which were difficult to be separated, the linear elution
method of separation with good effect was used to separate the products.