Density functional theory calculations were conducted to elucidate the mechanism, selectivity, and the origin of Rh₂(oct)₄ ([Rh])-catalyzed O–H/C–H insertion reactions of 1,3-diketones. For three different 1,3-diketone substrates (acetylacetone, 2-methylcyclohexane-1,3-dione, and cyclic 1,3-diketone), two different insertion modes O–H and C–H and three mechanisms were investigated under [Rh]-assisted, 2H₂O-assisted, and [Rh]-nH₂O (n = 1–3) co-assisted conditions. The computational results indicated that the [Rh]-2H₂O co-assisted ones are the most favored cases. The corresponding rate-determining steps are the concerted C–N bond formation and H-shift process with an energy barrier of 20.4, 22.6, and 25.1 kcal mol⁻¹, respectively. More importantly, it was found that water molecules can significantly improve the activity of the [Rh] catalyst and lower the free energy barrier. The distortion/interaction and natural bond orbital analyses suggested that the interaction energy is the dominant factor determining the difference of the reaction between three 1,3-diketones and the α-imino Rh(II) carbenoids. The chemoselectivity of the O–H/C–H insertion reactions of three different 1,3-diketone substrates depends on three factors: steric repulsion, the distortion of substrates, and electronic effects. Our findings can serve as a benchmark for other similar [Rh]-catalyzed reactions, which might open a new avenue for designing more efficient O–H/C–H insertion reactions.

中文翻译：

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dirhodium （ii）类胡萝卜素催化底物控制的竞争性O–H和C–H插入反应的计算机理研究：了解化学选择性的起源†

进行密度泛函理论计算以阐明机理，选择性和Rh ₂（oct）₄（[Rh]）催化的1,3-二酮O-H / C-H插入反应的起源。对于三种不同的1,3-二酮底物（乙酰丙酮，2-甲基环己烷-1,3-二酮和环状1,3-二酮），在[Rh]下研究了两种不同的插入模式OH和CH，以及三种机理]辅助，2H ₂ O辅助和[Rh] -n H ₂ O（n = 1-3）共同辅助条件。计算结果表明，[Rh] -2H ₂O共同协助的案例是最受青睐的案例。相应的速率确定步骤是协调的C–N键形成和H位移过程，其能垒分别为20.4、22.6和25.1 kcal mol ^-1。更重要的是，发现水分子可以显着提高[Rh]催化剂的活性并降低自由能垒。变形/相互作用和自然键轨道分析表明，相互作用能是决定三个1,3-二酮与α-亚氨基Rh（II）类胡萝卜素。三种不同的1,3-二酮底物的O–H / C–H插入反应的化学选择性取决于三个因素：空间排斥，底物的变形和电子效应。我们的发现可以作为其他类似的[Rh]催化反应的基准，这可能为设计更有效的O–H / C–H插入反应开辟新途径。