【作者】 王维；

【导师】 佘远斌；

【作者基本信息】 北京工业大学 ， 应用化学， 2013， 博士

【摘要】 芳醛是重要的有机合成中间体，广泛应用于合成医药、农药、染料、香精香料、香水等。芳醛的制备方法很多，其中以邻/对甲酚最为廉价易得，但目前以邻/对甲酚为原料的方法存在环境污染严重、能耗高、合成效率低的问题。而且，由于甲酚中的－CH₃受到取代基的影响，使其氧化条件的选择尤为关键，若采用剧烈的氧化条件则会导致深度氧化，进而使产物的选择性变差；若选择过于缓和的条件又不能将其氧化或导致原料的转化率过低。氧气作为价廉易得、清洁无污染的氧化剂，如能用其直接氧化烷基芳烃，高收率地得到芳醛，无疑将成为前景光明的绿色化工新技术。但在温和条件下，氧分子的基态为三线态，与基态为单线态的烷基芳烃之间反应在能量和自旋上是禁阻的，需要采用高效催化剂活化分子氧，才能最大限度地发挥氧气的氧化作用。金属卟啉类化合物能够从结构和功能上模拟细胞色素P-450，可在温和条件下活化分子氧，从而有效地解决上述反应自旋禁阻的问题。因此，本文致力于研究金属卟啉催化氧气氧化邻/对甲酚制备邻/对羟基苯甲醛的新方法及作用机制。首先设计合成了一系列轴向无氯配体和轴向带氯配体的对称（A₄型）及不对称（A₃B型）金属卟啉，并对其催化氧化邻/对甲酚的催化活性和选择性进行了系统深入的研究。同时，考察了金属卟啉-金属盐复合催化剂在对甲酚催化氧化反应中的催化活性和选择性。具体研究内容及结果如下：1、探讨了金属卟啉在对甲酚催化氧化反应中的性能和规律。通过研究具有不同结构的金属卟啉在上述反应中的催化作用，发现金属卟啉的催化活性大小顺序为铁卟啉>锰卟啉>钴卟啉；选择性顺序依次为铁卟啉>锰卟啉>钴卟啉；不同取代基的铁卟啉的活性和选择性顺序均为-CH₃O>-CH₃> H>-Cl>-NO₂；轴向无氯配体的金属卟啉和轴向带氯的金属卟啉对对甲酚转化率影响较小，而对对羟基苯甲醛选择性影响较大，其中以轴向带氯的金属卟啉为优。其中T（p-CH₃O）PPFeCl在对甲酚催化氧化反应中的活性最高，对甲酚的转化率可达78.7%，且对羟基苯甲醛选择性和收率分别为63.9%和50.3%。。2、探讨了金属卟啉-金属盐复合催化剂在对甲酚催化氧化制备对羟基苯甲醛反应中的规律。通过研究不同金属卟啉与金属盐复合体系在上述反应中的催化作用，发现金属卟啉与金属盐之间存在明显的协同效应，即少量金属卟啉与金属盐组成的复合催化剂可在更低的催化剂浓度和反应压力条件下进行，同时还可显著提高对甲酚的转化率及对羟基苯甲醛选择性和收率。其中T（p-CH₃O）PPFeCl-Co（OAc）2.4H2O的复合催化效果最好，与无催化剂（空白）相比，对甲酚的转化率可从8.0%提高到99.9%，对羟基苯甲醛的选择性可从17.4%提高到82.6%。而与单独使用金属卟啉相比，对甲酚的转化率提高了21.2%，对羟基苯甲醛的选择性提高了18.7%，且催化剂用量从之前的1.110mmol/L降低到0.279mmol/L。3、通过研究不同金属卟啉在邻甲酚催化氧化反应中的催化作用，发现该反应中金属卟啉的催化活性大小顺序为铁卟啉>锰卟啉>钴卟啉；选择性顺序依次为铁卟啉>钴卟啉>锰卟啉；不同取代基的铁卟啉中活性和选择性顺序均为-CH₃O>-CH₃> H>-Cl>-NO₂。其中T（p-CH₃O）PPFeCl在邻甲酚催化氧化反应的活性最高，得到邻甲酚的转化率为50.4%，且邻羟基苯甲醛选择性和收率分别为26.6%和13.4%。4、通过研究具有不同对称性的金属卟啉在催化氧化邻甲酚反应中的催化活性，发现A3B型金属卟啉较A₄型金属卟啉具有更高的催化活性，特别是不易变价的A3B型锌卟啉较相应的A₄型锌卟啉使得邻甲酚转化率提高了21.9%。通过量子化学计算A3B型金属卟啉和A₄型金属卟啉的微观结构和轨道能级，得到A3B型锌卟啉的ΔEH-L值小于相应的A₄型锌卟啉，使其在理论上更有利于轴向吸附及活化氧气，且具有更高的催化活性，计算得到的规律与实验结果规律相符。5、研究了邻/对甲酚氧化制备对羟基苯甲醛过程中各步反应的热力学，发现邻/对甲酚氧化反应中各步反应的△H均小于零，说明各步反应均为放热反应；各步反应的△G均为负值，说明各步反应在理论上均可自发进行；除邻羟基苯甲醚和对羟基苄甲醚生成反应外，其他各步反应△G均随温度的升高而升高，说明降低反应温度均有利于上述各步反应的进行。6、反应机理研究结果表明：金属卟啉催化氧气氧化对甲酚的反应为自由基反应。第一步由金属卟啉经过催化循环引发对甲酚产生烷基芳烃苄基自由基。第二步该自由基与分子氧结合生成过氧化物再进一步分解为醛；同时该自由基还可与三价金属－羟基络合物反应形成醌式结构。第三步该醌式结构分别与甲醇和水反应，形成对羟基苄甲醚和对羟基苯甲醇。第四步对羟基苯甲醇进一步氧化生成对羟基苯甲醛，对羟基苯甲醛可进一步深度氧化为对羟基苯甲酸。更多还原

【Abstract】 Aromatic aldehydes are important chemical intermediates for the synthesis ofvarious pharmaceuticals, pesticides, dyes, flavors, perfumes and chiral intermediates.There are many preparation methods for aromatic aldehydes, and directoxyfunctionalization of cresols at their benzylic positions provides an effectivemethod for synthesizing hydroxybenzaldehyde. However, conventional methods forpreparing o/p-hydrocybenzaldehydes have several disadvantages such as involvinglarge investment and high energy. In addition,-CH₃substituent of cresol can beinfluenced by other substituent to carry out deep oxidation under radical oxidationconditions, which cause the reduction of main product selectivity. While under mildconditions, cresols oxidation reactions might not carry out which influent the cresolconversion. Therefore, no doubt there will be a huge market if the aromatic aldehydescould be prepared from the direct catalytic oxidation of alkyl aromatics at highconversions and selectivities under mild conditions with dioxygen as economical andgreen oxidant. However, dioxygen exists in triplet state and hydrocarbons exist insinglet state, so the development and application of the above reaction are restrained,because the oxidation of hydrocarbons with molecular oxygen is spin-forbidden.Fortunately, metalloporphyrins can catalytically activate molecular oxygen even atmild temperature, so the spin-restrained problem of hydrocarbon oxidation is solved.Accordingly, this dissertation was focused on the study of the new method andoxidation mechenismof alkyl aromatics to aldehyde catalyzed by metalloporphyrinswith oxygen.A series of metalloporphyrins with or without axial ligand chloride weredesigned and synthesized firstly. Then, the conversions and selectivities of the abovemetalloporphyrins were studied systematically. Meawhile, the effect of the componentcatalysts between metalloporphyrins and metal salts on p-cresol oxidation reactionwere also studied. The main results are summarized as follows:1. Catalytic performance and rule of metalloporphyrins were investigated.Through the study of the catalytic effect of metalloporphyrins with different structuresin the above reaction, it was found that the catalytic activity order ofmetalloporphyrins in the reaction was iron porphyrin> manganese porphyrin> cobaltporphyrin; the order of selectivity of p-hydroxybenaldehyde was iron porphyrin>manganese porphyrin> cobalt porphyrin; the sequence of activity and selectivity ofiron porphyrins with different substitutes was-CH₃O>-CH₃>-H>-Cl>-NO₂; theaxial chlorine free ligand of metalloporphyrins did not effect the conversion ofp-cresol much, but for the selectivity of p-hydroxybenzaldehyde was influenced muchby the metalloporphyrins with and without axial chlorine, and the former oneperformed better on p-cresol conversion. Among the catalyst studied, T（p-CH₃O）PPFeCl performed the best, and78.7%conversion of p-cresol,63.9%selectivity and50.3%yield of p-hydroxybenzaldehyde were reached.2. The metalloporphyrins and metal salts co-catalysts were studied in thecatalytic oxidation of p-cresol to prepare p-hydroxybenzaldehyde. Through the studyof different metalloporphyrins and metal salts, it was found that there were obvioussynergistic effects between metalloporphyrins and metal salts. The oxidation ofp-cresol could carry out under lower reaction pressure with lower composite catalystsconcentration, meanwhile the p-cresol conversion and p-hydroxybenzaldehydeselectivity could be significantly improved. Among the composite catalysts studied,T（p-CH₃O）PPFeCl-Co（OAc）.4H2O performed best. The p-cresol conversion could beimproved from8.0%to99.9%, and the p-hydroxybenzaldehyde selectivity could beimproved from17.4%to82.6%, comparing with the reaction without catalyst.Comparing with the reaction results obtained by single metalloporphyrins, those usingcomposite catalysts could increase the conversion by21.2%andp-hydroxybenzaldehyde selectivity by18.7%. And also, the catalyst dosage wasreduced from1.110mmol/L to0.279mmol/L.3. Through the effect of different metalloporphyrins on the catalytic oxidationreaction of o-cresol, it was found that the catalytic activity order of metalloporphyrinsin the reaction was iron porphyrin> manganese porphyrin> cobalt porphyrin; the orderof selectivity of o-hydroxybenaldehyde was iron porphyrin> cobalt porphyrin>manganese porphyrin; the sequence of activity and selectivity of iron porphyrins withdifferent substitutes was-CH₃O>-CH₃>-H>-Cl>-NO₂. Among the catalyst studied,T（p-CH₃O）PPFeCl performed the best, and50.4%conversion of o-cresol,26.6%selectivity and13.4%yield of o-hydroxybenzaldehyde were reached.4. Through the studies on the catalytic activities of metalloporphyrins withdifferent symmetry on the o-cresol oxidation reaction, it was found that A₃B typemetalloporphyrins had better performances than A₄type metalloporphyrins, especiallyA₃B type zinc porphyrin which could increase the o-cresol conversion by21.9%. TheEHOMO, ELUMOand ΔEH-Lof A₃B type and A₄type metalloporphyrins were observedby the quantum chemistry calculation simulation, and the ΔEH-Lvalue of A₃B typezinc porphyrin was lower than that of A₄type zinc porphyrin, which explained thereason for the higher activity of A₃B type metalloporphyrins.5. The thermodynamics of preparation reaction of o/p-hydroxybenzaldehydefrom o/p-cresol were studied. It was found that, ΔH of all the steps of o/p-cresoloxidation reactions were below zero, indicating that the reactions were exothermicreaction; the ΔG of each step of o/p-cresol oxidation reactions was negative,indicating the reactions could be carried out spontaneously in theory; in addition,except for the ether formation reaction steps, ΔG of other steps of o/p-cresol oxidation reaction were increased with temperature rising, which indicated that lowertemperature was favorable to the steps above.6. The reaction mechanism study showed that the p-cresol oxidation reactioncatalyzed by metalloporphyrin was a free radical reaction. Firstly, the free radical ofalkyl aromatics was produced by the metalloporphyrin catalytic cycle. Secondly, thefree radicals reacted with molecular oxygen and formed peroxides, then furtherdecomposed into aldehydes; at the same time, the free radicals could also react withtrivalent metal hydroxy complexes to form quinoid structure. Thirdly, the quinoidstructure reacted with methanol or water to form p-hydroxylbenzylether orp-hydroxybenzylalcohol. Fourthly, p-hydroxybenzylalcohol further oxidized top-hydroxybenzaldehyde, and the aldehyde could be further oxidized top-hydroxybenzoic acid.更多还原