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首页> 外文期刊>Inorganic Chemistry: A Research Journal that Includes Bioinorganic, Catalytic, Organometallic, Solid-State, and Synthetic Chemistry and Reaction Dynamics >Activation of the C-H Bond by Electrophilic Attack: Theoretical Study of the Reaction Mechanism of the Aerobic Oxidation of Alcohols to Aldehydes by the Cu(bipy)2t/2,2,6,6-Tetramethylpiperidinyl-1-oxy Cocatalyst System
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Activation of the C-H Bond by Electrophilic Attack: Theoretical Study of the Reaction Mechanism of the Aerobic Oxidation of Alcohols to Aldehydes by the Cu(bipy)2t/2,2,6,6-Tetramethylpiperidinyl-1-oxy Cocatalyst System

机译：亲电攻击活化C-H键：Cu（bipy）2t / 2,2,6,6-四甲基哌啶基-1-氧基助催化剂体系对酒精进行好氧氧化成醛的反应机理的理论研究

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We have investigated the reaction mechanism of the selective aerobic oxidation of primary alcohols into aldehydes using a bipy-copper complex and the 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) radical as cocatalysts (Gamez et al. Chem. Commun. 2003, 2412-2415) and compared it to the well-known oxidation by the TEMPO+ ion. Our theoretical investigation shows that (a) the oxidation of alcohols to aldehydes by uncoordinated TEMPO+ takes place by electrophilic attack on the C-HR bond of the alcohol; (b) the Cu(bipy)2+ complex has two functions, namely, (1) it acts as a template that brings TEMPO and the (deprotonated) alcohol in proximity by coordinating these moieties in adjacent coordination sites, and (2) it oxidizes the TEMPO radical to (coordinated) TEMPO+ ion. The H abstraction from alcohol by TEMPO+ then proceeds as an intramolecular reaction, very much analogous to one of the reaction pathways with free TEMPO+ and with a remarkably low barrier. We stress that compared to other A-H bonds (A=C, N, O, F), the relatively high-lying C-H bonds are particularly susceptible to electrophilic attack, and notably the C-HR bond next to the O in an alcohol is so because it is pushed up by an O lone pair. Electrophilic attack, being common to the particular catalytic system studied in this paper and the well-known biotic and abiotic oxidation catalysis by heme and non-heme complexes of the ferryl (FeIVO2+) ion, appears to be a unifying electronic structure principle of C-HR hydroxylation and oxidation reactions.
机译：我们研究了使用联吡啶-铜配合物和2,2,6,6-四甲基哌啶基-1-氧基（TEMPO）自由基作为助催化剂将伯醇选择性好氧氧化为醛的反应机理（Gamez等，Chem。 Commun。2003，2412-2415），并将其与众所周知的TEMPO +离子氧化进行了比较。我们的理论研究表明：（a）不配位的TEMPO +将醇氧化为醛是通过亲电攻击醇的C-HR键而发生的; （b）Cu（bipy）2+配合物具有两个功能，即（1）它充当模板，通过在相邻的配位部位配位这些部分使TEMPO和（去质子化的）醇更接近，以及（2）将TEMPO自由基氧化为TEMPO +离子。然后通过TEMPO +从醇中提取H的过程是分子内反应，非常类似于具有游离TEMPO +和低阻隔的反应途径之一。我们强调，与其他AH键（A = C，N，O，F）相比，相对较高的CH键特别容易受到亲电子攻击，尤其是在醇中靠近O的C-HR键如此因为它被一个O孤对推上去。亲电子攻击是本文研究的特定催化系统的共同特征，也是众所周知的由亚铁（FeIVO2 +）离子的血红素和非血红素络合物进行的生物和非生物氧化催化，似乎是C-的统一电子结构原理HR羟基化和氧化反应。

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