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sp~3杂化的碳氢键氧化成酮是有机合成中一个重要方法.相应的酮产物被广泛应用在医药和天然产物合成中.目前已经开发出多种衍生于含N杂环酮的药物化合物和具有生物活性的天然产物,例如阿普米定、苯吡胺、氯苯吡胺、曲普利啶、多西拉敏等.传统的含N杂环侧链氧化生成酮的方法使用化学计量的强氧化剂(如高锰酸钾),不可避免地产生众多的副产物.近年来,均相的过渡金属催化剂被广泛应用于含N杂环侧链氧化生成酮的反应中.但是N杂环和过渡金属配位导致催化剂失活,选择性降低.金属的残留也使后处理过程变得繁琐.均相催化剂还存在难以回收利用的缺点.使用多相催化剂可以解决上述问题,因而具有重大的研究意义.目前为止,还很少有文献报道多相催化剂催化含N杂环侧链氧化生成酮的方法.本文使用硝酸锰和菲啰啉的络合物在氮气氛围中高温焙烧,制备了一系列新型MnO_x-N@C材料.首次应用于C–H氧化成酮的领域中.以2-苄基吡啶为模板底物,使用叔丁基过氧化氢为氧化剂,我们研究了MnO_x-N@C材料的催化活性.研究发现,在600oC焙烧得到的MnO_x-N@C材料具有最高的催化活性.实验得到最佳的反应条件:0.5mmol底物,3当量的叔丁基过氧化氢,1mgMnO_x-N@C(600oC)材料.ICP结果表明,1mgMnO_x-N@C(600oC)材料中含有的锰相对于0.5mmol底物的摩尔分数为0.79mol%,说明该材料具有很高的催化活性.我们进一步研究了MnO_x-N@C(600oC)材料适用的底物范围,发现它可以催化2,3-环戊烯并吡啶类化合物、苄基吡啶类化合物发生氧化反应生成相应的酮;当反应底物中存在其他可以被氧化的碳氢键时,该材料表现出很高的选择性,可见其具有广泛的底物范围和优异的选择性.对于克级以上规模的底物量,MnO_x-N@C仍能表现出很高的催化活性,表明其在有机合成中具有很好的实用性;连续使用6次后,该催化剂依然表现出很高的催化活性.表征结果表明,MnO_x-N@C(600oC)材料中MnO_x粒子大小为1.71–6.56nm;样品中存在C–N,C=N和吡咯型的N;Mn的化学态有+2,+3和+4.
The oxidation of sp ~ 3 hybrid hydrocarbon to ketone is an important method in organic synthesis. The corresponding ketone products are widely used in the synthesis of pharmaceuticals and natural products .A variety of drugs derived from N-containing ketones have been developed Compounds and biologically active natural products such as apramycin, pheniramine, chlorpheniramine, triprolididine, doxylamine, etc. The traditional method for the oxidation of side chains containing N-containing heterocycles to ketones uses stoichiometry Of the strong oxidants (such as potassium permanganate), inevitably produce a large number of by-products.In recent years, the homogeneous transition metal catalyst is widely used in the reaction of N-containing heterocyclic side chain oxidation ketones, but the N-heterocyclic And transition metal coordination led to the catalyst deactivation, selectivity decreased.Metal residue also make the post-processing process becomes cumbersome.Homogeneous catalysts also exist the shortcomings of difficult to recycle.Using heterogeneous catalysts can solve the above problems, and thus have a significant The research significance.So far, there are few reports of heterogeneous catalysts for catalytic N-containing heterocyclic side chain oxidation of ketone method.In this paper, the use of manganese nitrate and phenanthroline complex in high temperature calcination in nitrogen atmosphere, prepared A series of novel MnOx-N @ C materials were first used in the oxidation of C-H to ketones.Using t-butyl hydroperoxide as the substrate and 2-benzylpyridine as the template substrate, we investigated the effect of MnOx-N @ C material.The results showed that the MnOx-N @ C material calcined at 600oC had the highest catalytic activity.The optimal reaction conditions were obtained as follows: 0.5 mmol of substrate, 3 eq of t-butyl hydroperoxide, The results of ICP showed that the mole fraction of manganese contained in 1 mg MnOx-N @ C (600oC) with respect to 0.5 mmol substrate was 0.79 mol%, indicating that the material has high catalytic activity We further investigated the suitable substrate range of MnOx-N @ C (600oC) material and found that it can catalyze the oxidation of 2,3-cyclopenopyridines and benzylpyridines to the corresponding ketones. The material exhibits high selectivity when there are other hydrocarbon-hydrogen bonds that can be oxidized in the reaction substrate, showing a wide range of substrates and excellent selectivity.For Mn-x -N @ C can still show a high catalytic activity, indicating that it has good organic synthesis The results show that the size of MnO_x particles in MnO_x-N @ C (600oC) is 1.71-6.56nm. The presence of C-N, C = N and pyrrole-type N; the chemical states of Mn are +2, +3 and +4.