The oxidation of benzylic CH bonds by metalloporphyrins in supercritical carbon dioxide (scCO₂) has still limited. Herein, an efficient protocol of aerobic oxidation of primary benzylic CH bond by cobalt porphyrin and NHPI (N-hydroxyphthalimide) in scCO₂ was established. Using toluene as model substrate, 21.6% conversion and 81.2% benzoic acid selectivity was obtained under the optimized conditions. The protocol also exhibited good tolerance towards the oxidation of various substrates with different electron property groups. Moreover, a plausible mechanism involving free radical and high-valence cobalt species was proposed.

中文翻译：

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钴卟啉和 N-羟基邻苯二甲酰亚胺 (NHPI) 在超临界二氧化碳中催化氧化伯基 CH 键与分子氧

在超临界二氧化碳 (scCO ₂ ) 中，金属卟啉对苄基 CH键的氧化仍然有限。在此，建立了钴卟啉和 NHPI（N-羟基邻苯二甲酰亚胺）在 scCO ₂中对初级苄基 CH键进行有氧氧化的有效方案。以甲苯为模型底物，在优化条件下获得了21.6%的转化率和81.2%的苯甲酸选择性。该协议还对具有不同电子特性组的各种底物的氧化表现出良好的耐受性。此外，还提出了一种涉及自由基和高价钴物种的合理机制。