β-MnO2 nanoparticles as heterogenous catalysts for aerobic oxidative transformation of alcohols to carbonyl compounds, nitriles, and amides
β-MnO2 nanoparticles as heterogenous catalysts for aerobic oxidative transformation of alcohols to carbonyl compounds, nitriles, and amides
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β-MnO2 纳米粒子作为醇类有氧氧化转化为羰基化合物、腈类和酰胺类的多相催化剂
DOI：
10.1039/d2cy01476a
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发表时间：
2022
影响因子：
5
通讯作者：
Michikazu Hara
中科院分区：
文献类型：
--
作者：
Keigo Kamata;Nanami Kinoshita;Maki Koutani;Ryusei Aono;Eri Hayashi;Michikazu Hara
以NaMnO 4和廉价易得的KMnO 4为原料，采用层状锰氧化物前驱体，通过晶化法成功合成了高比表面积的β-MnO 2纳米粒子。这些β-MnO 2纳米粒子可以作为一种有效的和可重复使用的固体催化剂，用于以分子氧为唯一氧化剂的各种芳香和杂芳香醇的有氧氧化为相应的羰基化合物。在温和的反应条件下，β-MnO 2的催化活性高于其它锰基简单和复合氧化物催化剂。此外，本发明的氧化系统可以应用于在氨存在下醇到相应的腈和酰胺的一锅串联氧化转化，而不需要任何添加剂，如强碱和硝酰基自由基。结果表明，与α-MnO 2基OMS-2催化剂相比，β-MnO 2纳米粒子具有更高的氧化活性和更低的腈水合活性，是一种更有效的催化剂。包括腈水合中毒效应在内的机理研究表明，β-MnO 2和OMS-2之间的酸中心和晶体结构的差异可能分别影响腈和水的活化，从而导致β-MnO 2对腈合成的高选择性。
β-MnO2 nanoparticles with high specific surface areas were successfully synthesized by the crystallization of a layered manganese oxide precursor prepared using not only NaMnO4, but also inexpensive and easily available KMnO4. These β-MnO2 nanoparticles could function as an effective and reusable solid catalyst for the aerobic oxidation of various aromatic and heteroaromatic alcohols to the corresponding carbonyl compounds with molecular oxygen as the sole oxidant. β-MnO2 exhibited higher catalytic activity than other catalysts, including manganese-based simple and complex oxides under mild reaction conditions. In addition, the present oxidation system could be applied to the one-pot tandem oxidative transformation of alcohols to the corresponding nitriles and amides in the presence of ammonia, without the need for any additives such as strong bases and nitroxyl radicals. β-MnO2 nanoparticles were found to be more effective catalysts for the selective synthesis of nitriles from alcohols than the α-MnO2 based OMS-2 catalyst, likely due to the high oxidation activity and low nitrile hydration activity of β-MnO2. Mechanistic studies including the poisoning effects for nitrile hydration showed that the differences in acid sites and crystal structures between β-MnO2 and OMS-2 likely affect the activation of the nitriles and water, respectively, which leads to the high selectivity of β-MnO2 for nitrile synthesis.