ICMMO, Université Paris Sud, Université Paris Saclay, CNRS, 91405, Orsay Cedex, France.
Aix Marseille Université, Centrale Marseille, CNRS, ISM2 UMR 7313, 13397, Marseille, France.
Angew Chem Int Ed Engl. 2019 Nov 4;58(45):16023-16027. doi: 10.1002/anie.201907337. Epub 2019 Sep 25.
Using light energy and O for the direct chemical oxidation of organic substrates is a major challenge. A limitation is the use of sacrificial electron donors to activate O by reductive quenching of the photosensitizer, generating undesirable side products. A reversible electron acceptor, methyl viologen, can act as electron shuttle to oxidatively quench the photosensitizer, [Ru(bpy) ] , generating the highly oxidized chromophore and the powerful reductant methyl-viologen radical MV . MV can then reduce an iron(III) catalyst to the iron(II) form and concomitantly O to O in an aqueous medium to generate an active iron(III)-(hydro)peroxo species. The oxidized photosensitizer is reset to its ground state by oxidizing an alkene substrate to an alkenyl radical cation. Closing the loop, the reaction of the iron reactive intermediate with the substrate or its radical cation leads to the formation of two oxygenated compounds, the diol and the aldehyde following two different pathways.
利用光能和 O 直接氧化有机底物是一个主要的挑战。一个限制因素是使用牺牲电子供体通过还原猝灭光敏剂来激活 O，从而生成不需要的副产物。可逆电子受体，即甲紫精，可以作为电子穿梭体，将光敏剂 [Ru(bpy) ] 氧化猝灭，生成高度氧化的生色团和强还原剂甲紫精自由基 MV 。MV 可以将铁(III)催化剂还原为铁(II)形式，并同时将 O 在水介质中氧化为 O ，生成活性铁(III)-(过)氢氧物种。氧化后的光敏剂通过将烯烃底物氧化为烯基自由基阳离子，恢复到其基态。闭环反应中，铁反应中间体与底物或其自由基阳离子反应生成两种含氧化合物，二醇和醛，遵循两条不同的途径。
