Hypercoordinate iodine for catalytic asymmetric diamination of styrene: insights into the mechanism, role of solvent, and stereoinduction

Sreenithya, A.; Hadad, Christopher M.; Sunoj, Raghavan B.

doi:10.1039/c9sc01513b

Cited by 15 publications

(5 citation statements)

References 74 publications

(32 reference statements)

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“…The results showed that M06-2X calculated reaction barriers agree best with the experimentally derived values, with an error of less than 1 kcal/mol for both pathways (see Figure S1 and Tables S1 and S2 for detail). This is in agreement with previous computational studies from our group and others that the M06-2X method calculates kinetics and thermodynamics data close to experiments and is a suitable method to study organocatalytic reactions with multiple noncovalent interactions. ,− …”

Section: Computational Methodologysupporting

confidence: 91%

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?

2021

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The nucleophilic substitution mechanism of enantioselective allylation of α-chloro glycinate catalyzed by squaramide organocatalysts was studied using density functional theory. Based on a comprehensive study of S N 1 and S N 2 pathways of a catalyst-free reaction, we found that the catalytic reaction slightly favors the S N 1 mechanism, instead of the previously proposed S N 2 mechanism. Further investigation of different leaving groups and nucleophiles revealed that this is not limited to the present reaction, and the S N 1 mechanism might have been generally overlooked. For the squaramide-catalyzed reactions, the S N 1 mechanism was predicted to be preferred. However, the rate-determining step of the S N 1 pathway has changed from the chloride-leaving step to the C−C bond-formation step. Therefore, a first-order dependence on both substrates was predicted, in agreement with the observed second-order kinetics. Intriguingly, the lowestenergy enantioselective transition states (TSs) originate from different pathways; R-inducing TS corresponds to the S N 1 pathway, while S-inducing TS corresponds to S N 2. The calculated enantiomeric excesses of two squaramide catalysts agree well with the experimental values. Given the ubiquity of nucleophilic substitution reactions in chemistry and biology, we believe that our finding will inspire more studies that will lead to an improved mechanistic understanding of important chemical reactions, and it may even lead to better catalysts.

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Section: Computational Methodologysupporting

confidence: 91%

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?

2021

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“…Catalytic vicinal diamination of terminal styrenes was carried out in 3:1 MTBE/HFIP, whereas a 2:1 mixture of MTBE/TFE worked better for internal styrenes. In an effort to determine the source of stereoinduction for this hypercoordinate iodine-catalyzed vicinal diamination of styrenes, Sunoj and co-workers employed computational methods to investigate the mechanism of this transformation and to elucidate the role of HFIP on the reaction pathway (Scheme b) using an achiral hypercoordinate iodine species . Subsequently, the factors affecting the stereoinduction were delineated by examining the chiral hypercoordinate iodine species in the mechanism.…”

Section: Hypervalent Iodine Chemistrymentioning

confidence: 99%

HFIP in Organic Synthesis

et al. 2022

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1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) is a polar, strongly hydrogen bond-donating solvent that has found numerous uses in organic synthesis due to its ability to stabilize ionic species, transfer protons, and engage in a range of other intermolecular interactions. The use of this solvent has exponentially increased in the past decade and has become a solvent of choice in some areas, such as C–H functionalization chemistry. In this review, following a brief history of HFIP in organic synthesis and an overview of its physical properties, literature examples of organic reactions using HFIP as a solvent or an additive are presented, emphasizing the effect of solvent of each reaction.

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“…Notable asymmetric reactions developed include α-functionalization of ketones, difunctionalization of alkenes, oxidative dearomatization of phenols, and many others . However, stereochemical models and mechanistic discussions of these transformations are still in their infancy.…”

Section: Introductionmentioning

confidence: 99%

Mechanism and Origins of Enantioselectivities in Spirobiindane-Based Hypervalent Iodine(III)-Induced Asymmetric Dearomatizing Spirolactonizations

et al. 2019

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The work of Kita et al. on asymmetric oxidative dearomatization of naphthol carboxylic acids to spirolactones mediated/catalyzed by a novel, conformationally rigid μ-oxo-bridged hypervalent iodine(III) species is a landmark discovery in enantioselective iodine(III) catalysis [Kita, Y.; et al. Angew. Chem., Int. Ed. 2008, 47, 3787. DOI: 10.1002/anie.200800464; J. Am. Chem. Soc. 2013, 135, 4558. DOI: 10.1021/ja401074u]. We have investigated the detailed mechanism of this important transformation using density functional theory. Calculations revealed that proton transfer from the pendant carboxylic acid of naphthols to the bridging oxygen atom or the ligand of iodine(III) species, which enhances the nucleophilicity of the carboxylic oxygen and the nucleofugality of the iodoarene, is crucial for the dearomatizing spirolactonization. Halogen bonding between the resulting carboxylate and the electron-deficient iodine(III) center further stabilizes the dearomatizing spirolactonization transition states. Calculations also revealed a long-neglected cleaved μ-oxo iodine(III) species that is more reactive but less selective than the μ-oxo-bridged hypervalent iodine(III) species itself for the oxidative dearomatization of naphthols. The coexistence of two sequential dearomatizing spirolactonization processes in the reaction system results in a lower enantioselectivity. A new stereochemical model that is able to reproduce and rationalize the observed apparent enantioselectivities is proposed.

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Hypercoordinate iodine for catalytic asymmetric diamination of styrene: insights into the mechanism, role of solvent, and stereoinduction

Abstract: Stereoselectivity in the asymmetric diamination of styrene catalyzed by chiral hypercoordinate iodine originates from the prochiral face recognition when the substrate binds to the catalyst.

Cited by 15 publications

References 74 publications

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?

HFIP in Organic Synthesis

Mechanism and Origins of Enantioselectivities in Spirobiindane-Based Hypervalent Iodine(III)-Induced Asymmetric Dearomatizing Spirolactonizations

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Hypercoordinate iodine for catalytic asymmetric diamination of styrene: insights into the mechanism, role of solvent, and stereoinduction

Abstract: Stereoselectivity in the asymmetric diamination of styrene catalyzed by chiral hypercoordinate iodine originates from the prochiral face recognition when the substrate binds to the catalyst.

Cited by 15 publications

References 74 publications

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: SN1 or SN2 Mechanism, or Both?

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: SN1 or SN2 Mechanism, or Both?

HFIP in Organic Synthesis

Mechanism and Origins of Enantioselectivities in Spirobiindane-Based Hypervalent Iodine(III)-Induced Asymmetric Dearomatizing Spirolactonizations

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Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?

Asymmetric Nucleophilic Allylation of α-Chloro Glycinate via Squaramide Anion-Abstraction Catalysis: S_N1 or S_N2 Mechanism, or Both?