Acetophenone is an important industrial intermediate and generally produced by the Friedel-Crafts acylation reaction, suffering from a low reactivity and serious equipment corrosion. Direct oxidation of ethylbenzene to acetophenone by molecular oxygen will be benign and cost-effective. The catalytic performance of NHPI/Co(II) herein was investigated by selective oxidation of ethylbenzene to acetophenone in different solvents at room temperature. The solvent hexafluoropropan-2-ol (HFIP) was found to markedly enhance the transformation efficiency from ethylbenzene to acetophenone in comparison with acetic acid, pyridine and ethanol, and the ethylbenzene conversion and the selectivity to acetophenone was high up to 87.9 % and 61.2 %, respectively. A higher concentration of phthalimide-N-oxyl (PINO) radicals was observed by an in situ electron paramagnetic resonance spectrometer (EPR) in HFIP with respect to other solvents, suggesting that HFIP may facilitate the generation of the N-oxyl radical and thus promote the selective oxidation of ethylbenzene to acetophenone. Furthermore, the benzylic carbon radical (PhCHCH₃) from ethylbenzene was trapped by tetramethylpiperidine N-oxyl radical (TEMPO) and observed by a high resolution mass spectrometer. The findings of both PINO and PhCHCH₃ under reaction conditions indicated that the selective oxidation of ethylbenzene to acetophenone catalyzed by NHPI/Co(II) should proceed via a radical mode. The selective oxidation of ethylbenzene to acetophenone using molecular oxygen by NHPI/Co(II) in HFIP exhibited an important industrial application prospect.

苯乙酮是一种重要的工业中间体，通常由Friedel-Crafts酰化反应制得，反应活性低，设备腐蚀严重。分子氧将乙苯直接氧化为苯乙酮将是一种良性且具有成本效益的方法。通过在室温下在不同溶剂中将乙苯选择性氧化为苯乙酮，研究了本文的NHPI / Co（II）的催化性能。发现与溶剂乙酸，吡啶和乙醇相比，溶剂六氟丙烷-2-醇（HFIP）显着提高了乙苯到苯乙酮的转化效率，乙苯的转化率和对苯乙酮的选择性高达87.9％和61.2％ ， 分别。较高浓度的邻苯二甲酰亚胺-N-HFIP中的原位电子顺磁共振波谱仪（EPR）相对于其他溶剂观察到了羟基（PINO）自由基，这表明HFIP可以促进N-羟基自由基的生成，从而促进乙苯选择性氧化为苯乙酮。此外，来自乙苯的苄基碳自由基（PhCHC H ₃）被四甲基哌啶N-氧基自由基（TEMPO）捕获并通过高分辨率质谱仪观察。PINO和PhCHC H _3的发现在反应条件下表明，NHPI / Co（II）催化的乙苯选择性氧化为苯乙酮应通过自由基模式进行。NHPI / Co（II）在HFIP中利用分子氧将乙苯选择性氧化为苯乙酮具有重要的工业应用前景。