【作者】 赵博；

【导师】 任运来；

【作者基本信息】 河南科技大学 ， 有机化学， 2019， 硕士

【摘要】 C-H键广泛存在于有机物中,它们的转化为有机化合物的合成提供了广泛的选择。并且C-H键在官能化后只需浪费一个H原子,因此该类反应具有较高的原子经济性,在有机化学中有着重要的地位。近年来,C-H键的选择性氧化受到化学工作者的广泛关注。使用的氧化剂通常为双氧水、叔丁基过氧化氢、次氯酸钠、高锰酸钾以及三氧化铬等。与上述氧化剂相比,氧气较为清洁易得,这是因为它无毒,来源丰富,氧化后的产物往往是水,对环境污染小。然而由于氧分子中存在两个三电子键,具有一定的惰性,往往需要催化剂的参与才能发挥其氧化作用。在该类使用氧气为氧化剂的反应中,使用的催化剂通常为铜、铁、钌和锰等过渡金属。然而过渡金属在地球上的存量有限,具有一定的不可再生性,因此近年来2,2,6,6-四甲基哌啶氮氧化物、溴化氢、亚硝酸钠等非金属催化剂受到人们的青睐。基于这些现状,本论文以氮氧化物类非金属为催化剂,围绕苄基C-H键的需氧氧化,研究了苄醇类化合物向芳腈的转化,以及苄基醚向苯甲醛的转化。主要研究内容和结论如下:（1）以硝酸/2,2,6,6-四甲基哌啶氮氧化物（TEMPO）为催化剂体系,空气为氧化剂,醋酸铵为氮源,实现了苄醇向苯甲腈类化合物的转化。对催化剂种类、硝酸用量、温度、氮源、反应时间等条件进过一系列优化之后,结果表明反应的最佳条件为:30 mol%TEMPO、30 mol%硝酸、3当量的醋酸铵、2 mL冰醋酸为溶剂、50℃反应温度,1 atm空气、12 h反应时间。在最优反应条件下,研究了不同苄基醇类化合物的反应效果。结果表明芳环上所带的取代基对反应结果影响较小,不论是吸电子取代基的存在,还是带有给电子基团的苄醇几乎都可以顺利地进行反应,腈类产物的产率在60%-90%之间。该方法也能应用于较大位阻的底物,例如2,4-二氯苄醇和2,6-二氯苄醇的反应分别给出85%和75%的产率。2-萘甲醇也能有效地发生反应,以74%的产率得到2-萘甲腈产物。在增加硝酸用量到60%和减少TEMPO用量到20%的条件下,糠醇和羟甲基噻吩也能顺利地进行反应。而吡啶甲醇和脂肪醇无法转化为腈类产物。对反应机理进行了初步的研究,结果表明该反应过程为串联反应。在反应过程中,NO_x/TEMPO⁺为真正的催化物种。在这些催化物种的作用下,苯甲醇类化合物中的苄基C-H键与氧气反应,进行氧化脱氢,生成醛。然后醛类产物与醋酸铵中的[NH₄]反应生成亚胺。亚胺在NO_x/TEMPO⁺的催化作用下进行氧化脱氢,得到苯甲腈类目标产物。（2）以硝酸为催化剂,氧气为氧化剂,六氟异丙醇为溶剂,实现了苄基甲基醚类化合物中C-H键的氧化,得到苯甲醛类化合物。2对氮氧化物、温度、时间、反应气氛以及硝酸用量等条件进行了优化,结果表明反应的最佳条件为,20mol%硝酸、六氟异丙醇为溶剂、1atm氧气、30 h反应时间。在最优反应条件下,研究了不同苄基醚类化合物的反应效果。结果表明苯环上连有甲基、叔丁基、氟、氯、溴基团时,反应能够很好地进行,得到的目标产物的产率为66%-90%。而以带甲氧基或氰基取代的苄基醚为底物时,仅得到微量的目标产物。此外,苄基十二烷基醚和苄基环己基醚也能有效地进行反应,得到较高产率的醛类产物。更多还原

【Abstract】 C-H bonds widely exist in organic compounds and their conversion provides a broad pathway for the synthesis of organic compounds.Moreover,only one hydrogen atom in the C-H bond is wasted after it is functionalized,so this kind of reaction has a characteristic of high atomic economy and plays an important role in organic chemistry.In recent years,chemists have already paid extensive attention to the selective oxidation of C-H bonds,where various oxidants such as hydrogen peroxide,t-butyl hydroperoxide,sodium hypochlorite,potassium permanganate,chromium trioxide and so on are commonly used.Compared with the above-mentioned oxidants,oxygen is more environment-friendly and easy to be obtained because it is non-toxic,rich in the nature,and the oxidative product is water,which is less pollution to the environment.But,the molecular oxygen is less reactive towards most organic molecules because it exists in the inactive triplet ground state.So it is usually depends on the catalysis transition metals such as copper,iron,ruthenium,manganese and so on.But the amount of transition metals on the earth are limited and non-renewable.Non-metallic catalysts such as 2,2,6,6-tetramethylpiperidine oxynitride and hydrogen bromide/sodium nitrite have been widely favored in recent years.Based on these current conditions,we studied the conversion of benzyl alcohol compounds to aromatic nitrile and the conversion of benzyl ethers to benzaldehydes by using nitrogen oxides as catalysts.The main research contents and conclusions are as follows:（1）The conversion of benzyl alcohol to benzonitrile was achieved by using nitric acid/2,2,6,6-tetramethylpiperidine-1-oxyl（TEMPO）as the catalyst system,air as the oxidant and ammonium acetate as the nitrogen source.We optimized the critical parameters including the catalyst,the dosage of nitric acid,temperature,nitrogen source,reaction time and other conditions,the results showed that the optimal conditions for the reaction were as follows:30 mol%nitric acid,30 mol%TEMPO,3equiv.ammonium acetate,and glacial acetic acid as solvent,reaction temperature is50°C,1 atm air,reaction time is 12 h.We set out to evaluate the scope of this strategy under the optimal reaction conditions.The results showed that the electronic nature of the substituents had less effect on the reaction,because either the electron-withdrawing substituents or the benzyl alcohol with electron-donating groups can be smoothly reacted.The yield of nitrile products was between 60%and 90%.This method can also be applied to substrates with larger steric hindrance,such as the reaction of 2,4-dichlorobenzyl alcohol and 2,6-dichlorobenzyl alcohol,the yields of the nitrile products being 85%and 75%,respectively.Naphthalene methanol can also react efficiently for the 2-naphthonitrile was obtained in 74%yield.The furfuryl alcohol and 2-thiophenemethanol also react smoothly when the amount of nitric acid was increased to 60%and the amount of TEMPO was decreased to 20%.Pyridine methanol and fatty alcohol cannot be converted to nitrile products.Preliminary mechanistic investigation suggests that the present transformation is a stepwise reaction.The true catalytic species of the reaction is NO_x/TEMPO⁺.Under the action of these catalytic species,the benzyl C-H bond in benzyl alcohol reacts with oxygen to undergo oxidative dehydrogenation to form an aldehyde.The aldehyde product is reacted with[NH₄]in ammonium acetate to form the imine.The imine is oxidatively dehydrogenated under the catalysis of NO_x/TEMPO⁺to obtain a benzonitrile target product.（2）By using nitric acid as the catalyst,oxygen as the oxidant,and hexafluoroisopropanol as the solvent,the oxidation of the C-H bond in the benzyl methyl ether compound was achieved and a benzaldehyde compound was obtained.Optimization of the reaction solvent showed that the use of hexafluoroisopropanol was the key to the efficient reaction,which allowed the reaction to proceed at room temperature.After a series of optimizations the conditions of nitrogen oxides,temperature,time,reaction atmosphere and nitric acid dosage.The results showed that the optimal conditions for the reaction were:20 mol%nitric acid,hexafluoroisopropanol as solvent,1 atm oxygen,reaction time is 30 h.We set out to evaluate the scope of this strategy under the optimal reaction conditions.The results showed that when a methyl,tert-butyl,fluorine,chlorine or bromine group was attached to the benzene,the reaction proceeds well,and the yield of the target product obtained was from 66%to 90%.When a benzyl ether substituted with a methoxy group or a cyano group was used as a substrate,only a small amount of the target production was obtained.Furthermore,benzyl 1-dodecyl ether and Benzyl cyclohexyl ether were also efficiently reacted to obtain aldehyde products in 90%and94%yields,respectively.更多还原