ﾎ�-MnO2 nanoparticles with high sp. 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 ﾎｲ-MnO2 nanoparticles could function as an effective and reusable solid catalyst for the aerobic oxidation of various aromatic and heteroaromatic alcs. to the corresponding carbonyl compounds with mol. oxygen as the sole oxidant. ﾎｲ-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 was applied to the one-pot tandem oxidative transformation of alcs. to the corresponding nitriles and amides in the presence of ammonia, without the need for any additives such as strong bases and nitroxyl radicals. ﾎｲ-MnO2 nanoparticles were found to be more effective catalysts for the selective synthesis of nitriles from alcs. than the ﾎｱ-MnO2 based OMS-2 catalyst, likely due to the high oxidation activity and low nitrile hydration activity of ﾎｲ-MnO2. Mechanistic studies including the poisoning effects for nitrile hydration showed that the differences in acid sites and crystal structures between ﾎｲ-MnO2 and OMS-2 likely affect the activation of the nitriles and water, resp., which leads to the high selectivity of ﾎｲ-MnO2 for nitrile synthesis.
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