Wang Xinliang, Liu Renhua, Jin Yu, Liang Xinmiao
Dalian Institute of Chemical Physics, Institution Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, PR China.
Chemistry. 2008;14(9):2679-85. doi: 10.1002/chem.200701818.
Hydrochloric acid, a very inexpensive and readily available inorganic acid, has been found to cooperate exquisitely with NaNO(2)/TEMPO in catalyzing the molecular-oxygen-driven oxidation of a broad range of alcohol substrates to the corresponding aldehydes and ketones. This transition-metal-free catalytic oxidative conversion is novel and represents an interesting alternative route to the corresponding carbonyl compounds to the metal-catalyzed aerobic oxidation of alcohols. The reaction is highly selective with respect to the desired product when carried out at room temperature in air at atmospheric pressure. Notably, the use of very inexpensive NaNO(2) and HCl in combination with TEMPO for this highly selective aerobic oxidation of alcohols in air at ambient temperature makes the reaction operationally and economically very attractive. The results of mechanistic studies, performed with the aid of electrospray ionization mass spectrometry (ESI-MS), are presented and discussed. TEMPO, TEMPOH, and TEMPO(+) were observed in the redox cycle by means of ESI-MS. On the basis of these observations, a mechanism is proposed that may provide an insight into the newly developed aerobic alcohol oxidation.
盐酸是一种非常廉价且容易获得的无机酸，已发现它能与亚硝酸钠（NaNO₂）/2,2,6,6-四甲基哌啶氮氧化物（TEMPO）完美配合，催化多种醇底物在分子氧驱动下氧化为相应的醛和酮。这种无过渡金属的催化氧化转化是新颖的，代表了一种与金属催化的醇类需氧氧化不同的、通往相应羰基化合物的有趣替代途径。当在室温、常压空气中进行反应时，该反应对所需产物具有高度选择性。值得注意的是，使用非常廉价的亚硝酸钠和盐酸与TEMPO相结合，在环境温度下于空气中对醇进行这种高度选择性的需氧氧化，使得该反应在操作和经济方面都非常有吸引力。本文展示并讨论了借助电喷雾电离质谱（ESI-MS）进行的机理研究结果。通过ESI-MS在氧化还原循环中观察到了TEMPO、TEMPOH和TEMPO⁺。基于这些观察结果，提出了一种机理，该机理可能有助于深入了解新开发的需氧醇氧化反应。
