Revisiting the effect of <scp><i>f</i></scp>‐functions in predicting the right reaction mechanism for hypervalent iodine reagents

Sun, Tianyu; Chen, Kai; Zhou, Huakang; You, Tingting; Yin, Penggang; Wang, Xiao

doi:10.1002/jcc.26469

Cited by 14 publications

(15 citation statements)

References 43 publications

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“…For an optimal balance between computational cost and accuracy, the M06‐2X [10,51] exchange functional was combined with the Def2‐TZVP [52] basis set for all atoms, except iodine for which Def2‐TZVPD [53] and its associated effective‐core potential [54] was utilized to account for relativistic effects. This model chemistry was successfully employed in the study of the isomerization mechanism of Togni I and II reagents [32,55] and it is consistent with the SMD18 parameterizations [50b] . An ultra‐fine grid and a tight geometry optimization criterium were utilized in all calculation.…”

Section: Methodsmentioning

confidence: 93%

Relating Bond Strength and Nature to the Thermodynamic Stability of Hypervalent Togni‐Type Iodine Compounds

et al. 2021

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The bond strength and nature of a set of 32 Togni‐like reagents have been investigated at the M062X/def2‐TZVP(D) level of theory in acetonitrile described with the SMD continuum solvent model, to rationalize the main factors responsible for their thermodynamic stability in different conformations, and trifluoromethylation capabilities. For the assessment of bond strength, we utilized local stretching force constants and associated bond strength orders, complemented with local features of the electron density to access the nature of the bonds. Bond dissociation energies varied from 31.6 to 79.9 kcal/mol depending on the polarizing power of the ligand trans to CF3. Based on the analysis of the Laplacian of the density, we propose that the charge‐shift bond character plays an important role in the stability of the molecules studied, especially for those containing I−O bonds. New insights on the trans influence and on possible ways to fine‐tune the stability of these reagents are provided.

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Section: Methodsmentioning

confidence: 93%

Relating Bond Strength and Nature to the Thermodynamic Stability of Hypervalent Togni‐Type Iodine Compounds

et al. 2021

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“…All the quantum chemical calculations were carried out with the Gaussian 09 package using an ultrafine grid . Recent computational studies and the benchmark work of Schaefer and co-workers have demonstrated that the hybrid-meta GGA functional M06-2X was suitable for hypervalent iodine mediated reactions . Accordingly, optimizations of the geometries of minima and transition states (TSs) were carried out at the M06-2X/6-31G(d,p)-SDD(I) level of theory .…”

Section: Methodsmentioning

confidence: 99%

Catalyst-Substrate Helical Character Matching Determines the Enantioselectivity in the Ishihara-Type Iodoarenes Catalyzed Asymmetric Kita-Dearomative Spirolactonization

et al. 2023

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Catalyst design has traditionally focused on rigid structural elements to prevent conformational flexibility. Ishihara’s elegant design of conformationally flexible C 2-symmetric iodoarenes, a new class of privileged organocatalysts, for the catalytic asymmetric dearomatization (CADA) of naphthols is a notable exception. Despite the widespread use of the Ishihara catalysts for CADAs, the reaction mechanism remains the subject of debate, and the mode of asymmetric induction has not been well established. Here, we report an in-depth computational investigation of three possible mechanisms in the literature. Our results, however, reveal that this reaction is best rationalized by a fourth mechanism called “proton-transfer-coupled-dearomatization (PTCD)”, which is predicted to be strongly favored over other competing pathways. The PTCD mechanism is consistent with a control experiment and further validated by applying it to rationalize the enantioselectivities. Oxidation of the flexible I(I) catalyst to catalytic active I(III) species induces a defined C 2-symmetric helical chiral environment with a delicate balance between flexibility and rigidity. A match/mismatch effect between the active catalyst and the substrate’s helical shape in the dearomatization transition states was observed. The helical shape match allows the active catalyst to adapt its conformation to maximize attractive noncovalent interactions, including I(III)···O halogen bond, N–H···O hydrogen bond, and π···π stacking, to stabilize the favored transition state. A stereochemical model capable of rationalizing the effect of catalyst structural variation on the enantioselectivities is developed. The present study enriches our understanding of how flexible catalysts achieve high stereoinduction and may serve as an inspiration for the future exploration of conformational flexibility for new catalyst designs.

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“…To validate the accuracy of the SMD/M06-2X/def2-TZVP//SMD/M06-2X/LANL2DZ(d),6-31G(d) calculations in determining the relative energies of species, we optimized key structures related to the PhI(O)(OAc) 2 -mediated oxidation of p -nitrophenol using the triple-zeta def2-TZVP Ahlrich’s basis set (BS2); this basis set was recently reported by Sun et al as a suitable one for the optimization of species formed during oxidative reactions mediated by IBX . These additional results demonstrate that the basis set dependence of the geometries is insignificant in affecting the final results.…”

Section: Methodsmentioning

confidence: 99%

Oxidation of Electron-Deficient Phenols Mediated by Hypervalent Iodine(V) Reagents: Fundamental Mechanistic Features Revealed by a Density Functional Theory-Based Investigation

et al. 2021

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Hypervalent iodine (HVI) compounds are efficient reagents for the double oxidative dearomatization of electron-rich phenols to o-quinones. We recently reported that an underexplored class of iodine(V) reagents possessing bidentate bipyridine ligands, termed Bi(N)-HVIs, could dearomatize electron-poor phenols for the first time. To understand the fundamental mechanistic basis of this unique reactivity, density functional theory (DFT) was utilized. In this way, different pathways were explored to determine why Bi(N)-HVIs are capable of facilitating these challenging transformations while more traditional hypervalent species, such as 2-iodoxybenzoic acid (IBX), cannot. Our calculations reveal that the first redox process is the rate-determining step, the barrier of which hinges on the identity of the ligands bound to the iodine(V) center. This crucial process is composed of three steps: (a) ligand exchange, (b) hypervalent twist, and (c) reductive elimination. We found that strong coordinating ligands disfavor these elementary steps, and, for this reason, HVIs bearing such ligands cannot oxidize the electron-poor phenols. In contrast, the weakly coordinating triflate ligands in Bi(N)-HVIs allow for the kinetically favorable oxidation. It was identified that trapping in situ-generated triflic acid is a key role played by the bidentate bipyridine ligands in Bi(N)-HVIs as this serves to minimize the decomposition of the ortho-quinone product.

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Revisiting the effect of f‐functions in predicting the right reaction mechanism for hypervalent iodine reagents

Cited by 14 publications

References 43 publications

Relating Bond Strength and Nature to the Thermodynamic Stability of Hypervalent Togni‐Type Iodine Compounds

Relating Bond Strength and Nature to the Thermodynamic Stability of Hypervalent Togni‐Type Iodine Compounds

Catalyst-Substrate Helical Character Matching Determines the Enantioselectivity in the Ishihara-Type Iodoarenes Catalyzed Asymmetric Kita-Dearomative Spirolactonization

Oxidation of Electron-Deficient Phenols Mediated by Hypervalent Iodine(V) Reagents: Fundamental Mechanistic Features Revealed by a Density Functional Theory-Based Investigation

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