Stereoretention in styrene heterodimerisation promoted by one-electron oxidants

Zhang, Xinglong; Paton, Robert S.

doi:10.1039/d0sc03059g

Cited by 12 publications

(12 citation statements)

References 117 publications

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“…The authors later extended their method to the construction of highly functionalized cyclobutanes with complementary all- trans and trans – cis – trans relative stereochemistry via PIDA-catalyzed intramolecular dimerization of silicon-tethered alkenes and bis-allylethers in HFIP . The influence of the cis - and trans -configuration of the alkene on the stereochemical outcome of the transformation was investigated computationally . Additional exploration of the reaction mechanism focused on the initially proposed bimolecular single-electron reduction of the hypervalent iodine reagent, which was unfavored.…”

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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Section: Hypervalent Iodine Chemistrymentioning

confidence: 99%

HFIP in Organic Synthesis

et al. 2022

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“…All calculations were carried out at the MN15/def2-TZVPPD/SMD//MN15/6-31+G(d,p)+SDD(Au)/SMD level of theory, with implicit solvation . Paton’s parameters were used to manually define HFIP using the SMD model . The def2-TZVPPD basis set was obtained from the Basis Set Exchange .…”

Section: Resultsmentioning

confidence: 99%

“…87 Paton's parameters were used to manually define HFIP using the SMD model. 88 The def2-TZVPPD basis set was obtained from the Basis Set Exchange. 89 Energies quoted are free energies relative to [AuCl(IPr)] (1) and include a +1.89 kcal/mol correction to reflect a 1 mol/L rather than 1 atm state.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Hexafluoroisopropanol (HFIP) as a Multifunctional Agent in Gold-Catalyzed Cycloisomerizations and Sequential Transformations

et al. 2023

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Despite the unique position of gold catalysis in contemporary organic synthesis, this area of research is notorious for requiring activators and/or additives that enable catalysis by generating cationic forms of gold catalysts. Cycloisomerization reactions occupy a significant portion of the gold-catalyzed reaction space, while they represent a diverse family of reactions that are frequently utilized in synthesis. Herein, hexafluoroisopropanol (HFIP) is shown to be a uniquely simple tool for gold-catalyzed cycloisomerizations, rendering the use of external activators obsolete and leading to highly active catalytic systems with ppm levels of catalyst loading in certain cases. HFIP assumes a dual role as a solvent and an activator, operating via the dynamic activation of the Au−Cl bond through hydrogen bonding, which initiates the catalytic cycle. This special mode of catalysis can enable efficient and scalable cyclization reactions of propargylamides and ynoic acids with simple [AuCl(L)] complexes. A thorough screening of ancillary ligands and counter anions has been performed, establishing this methodology as an alternative to elaborate ligand/catalyst design and to the use of activators. Additionally, this concept is applied in C−C bond-forming cycloisomerization reactions leading to 2H-chromenes and to the design of catalytic systems for sequential or one-pot transformations leading to activated ketoesters, a functionalized N-heterocyclic carbene (NHC) precursor salt, and a compound bearing the bioactive indole core, among others. Importantly, through mechanistic investigations, including a "snapshot" of the species of interest in the solid state, we were able to unambiguously detect the key H-bonding interaction between HFIP and the gold catalyst, shedding light on the intermolecular mode of activation that enables catalysis. In the cases examined herein, HFIP is not only an excellent solvent but also a potent activator and a valuable synthetic handle when incorporated into functional groups of products.

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“…Therefore, we herein interpret DFT simulations on the HOMD and HETD that gives all‐ trans cyclobutane under HVIRs with PIDA and DMP , respectively, featuring (1) the nature of initiation whether one or two‐electron reduction with considerations involved the effect of HFIP on the reactivity of this protocol, and (2) realizing the dynamical nature of homo‐ and heterodimerization via quasiclassical trajectory molecular dynamics (QCTMD) simulations. [ 51b ]…”

Section: Introductionmentioning

confidence: 99%

“…A recent computational study reported by Zhan and Paton has evaluated the stereoretention in the styrene heterodimerization promoted by a single‐electron oxidant. [ 51a ] However, the nature of initiation in the dimerization was incomplete. Therefore, we herein interpret DFT simulations on the HOMD and HETD that gives all‐ trans cyclobutane under HVIRs with PIDA and DMP , respectively, featuring (1) the nature of initiation whether one or two‐electron reduction with considerations involved the effect of HFIP on the reactivity of this protocol, and (2) realizing the dynamical nature of homo‐ and heterodimerization via quasiclassical trajectory molecular dynamics (QCTMD) simulations.…”

Section: Introductionmentioning

confidence: 99%

Hypervalent Iodine‐Mediated Styrene Hetero‐ and Homodimerization Initiation Proceeds with Two‐Electron Reductive Cleavage

Hussein

Al-Yasari

2020

Eur J Org Chem

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A mechanistic insight into the hetero‐ and homodimerizations (HETD and HOMD) of styrenes promoted by hypervalent iodine reagents (HVIRs; DMP and PIDA) and facilitated by hexafluoro2‐propanol (HFIP) to yield all‐trans cyclobutanes is reported using density functional theory (DFT) calculations. The initialization involving direct bimolecular one‐electron transfer is found to be highly unfavored, especially for the PIDA system. At this point, we suggest that the reaction is initiated with an overall two‐electron reductive cleavage of two I–O bond cleavages, affording I(III) (iodinane) and I(I) (iodobenzene) product with DMP and PIDA as oxidant, respectively. The resulting acetate groups are stabilized by the solvent HFIP through strong hydrogen bonding interaction, which promotes the electron transfer process. The nature of the electron transfer is studied in detail and found that the overall two‐electron transfer occurs within a trimolecular complex organized by π‐stacking interactions and as a stepwise and concerted mechanism for I(III) and I(V) oxidants, respectively. The reaction rate is determined by the initialization step: for I(III), the initiation is thermodynamically endergonic, whereas the endergonicity for I(V) is modest. Upon initialization, the reaction proceeds through a stepwise [2+2] pathway, involving a radical‐cationic π–π stacked transition states, where the HOMD is a dynamically competing pathway to HETD although the latter is relatively faster.

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Stereoretention in styrene heterodimerisation promoted by one-electron oxidants

Abstract: Radical cations generated from the oxidation of C=C p-bonds are synthetically useful reactive intermediates for C–C and C–X bond formation. Radical cation formation, induced by sub-stoichiometric amounts of external oxidant,...

Cited by 12 publications

References 117 publications

HFIP in Organic Synthesis

HFIP in Organic Synthesis

Hexafluoroisopropanol (HFIP) as a Multifunctional Agent in Gold-Catalyzed Cycloisomerizations and Sequential Transformations

Hypervalent Iodine‐Mediated Styrene Hetero‐ and Homodimerization Initiation Proceeds with Two‐Electron Reductive Cleavage

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