Lewis acid catalyzed heavy atom tunneling – the case of 1<i>H</i>-bicyclo[3.1.0]-hexa-3,5-dien-2-one

Henkel, Stefan; Merini, Melania Prado; Mendez‐Vega, Enrique; Sander, Wolfram

doi:10.1039/d1sc02853g

Cited by 13 publications

(20 citation statements)

References 35 publications

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“…P.Mendez-VegaE.SanderW. Henkel, S. Merini, M. P. Mendez-Vega, E. Sander, W. Chem. Sci.2021121101311019 …”

Section: Key Referencesmentioning

confidence: 99%

“…As discussed in the previous section on the Cope rearrangement of semibullvalenes, solid state effects are likely at play in addition to solvation on a local or global level. To address the effect of local solvation, experiments that allowed for the selective formation of 1:1 complexes of BHD with Lewis acids (H 2 O, ICF 3 or BF 3 ) and the subsequent monitoring of their respective tunneling kinetics were performed …”

Section: Heavy-atom Tunneling With High Exothermicity: 1h-bicyclo[310...mentioning

confidence: 99%

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Solvation Effects on Quantum Tunneling Reactions

et al. 2022

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Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: A decisive factor for obtaining high yields and selectivities in organic synthesis is the choice of the proper solvent. Solvent selection is often guided by the intuitive understanding of transition state−solvent interactions. However, quantummechanical tunneling can significantly contribute to chemical reactions, circumventing the transition state and thus depriving chemists of their intuitive handle on the reaction kinetics. In this Account, we aim to provide rationales for the effects of solvation on tunneling reactions derived from experiments performed in cryogenic matrices.The tunneling reactions analyzed here cover a broad range of prototypical organic transformations that are subject to strong solvation effects. Examples are the hydrogen tunneling probability for the cis−trans isomerization of formic acid which is strongly reduced upon formation of hydrogen-bonded complexes and the [1,2]H-shift in methylhydroxycarbene where a change in product selectivity is predicted upon interaction with hydrogen bond acceptors. Not only hydrogen but also heavy atom tunneling can exhibit strong solvent effects. The direction of the nearly degenerate valence tautomerization between benzene oxide and oxepin was found to reverse upon formation of a halogen or hydrogen bond with ICF 3 or H 2 O. But even in the absence of strong noncovalent interactions such as hydrogen or halogen bonding, solvation can have a decisive effect on tunneling as evidenced by the Cope rearrangement of semibullvalenes via heavy-atom tunneling. Can quantum tunneling be catalyzed? The acceleration of the ring expansion of 1H-bicyclo[3.1.0.]-hexa-3,5-dien-2-one by complexation with Lewis acids provides a proof-of-concept for tunneling catalysis. Two concepts are central for the explanation and prediction of solvation effects on tunneling phenomena: a simple approach expands the Born−Oppenheimer approximation by separating nuclear degrees of freedom into intra-and intermolecular degrees. Intermolecular movements represent the slowest motions within molecular aggregates, thus effectively freezing the position of the solvent in relation to the reactant during the tunneling process. Another useful approach is to treat reactants and products by separate single-well potentials, where the intersection represents the transition state. Thus, stabilization of the reactants via solvation should result in an increase in barrier heights and widths which in turn lowers tunneling probabilities. These simple models can predict trends in tunneling kinetics and provide a rational basis for controlling tunneling reactions via solvation.

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“…P.Mendez-VegaE.SanderW. Henkel, S. Merini, M. P. Mendez-Vega, E. Sander, W. Chem. Sci.2021121101311019 …”

Section: Key Referencesmentioning

confidence: 99%

Section: Heavy-atom Tunneling With High Exothermicity: 1h-bicyclo[310...mentioning

confidence: 99%

Solvation Effects on Quantum Tunneling Reactions

et al. 2022

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“…95,96 About a dozen examples of direct spectroscopic observation of carbon-atom QMT occurring under matrix isolation conditions have been reported. [96][97][98][99][100] In recent investigations, we have also discovered a new and distinctive case of a heavy-atom QMT reaction involving the displacement of both nitrogen and oxygen atoms. 101 The 2-formyl-3-fluorophenylazide precursor, which was designed to achieve stabilization of the syn-aldehyde conformation, allows generation of the corresponding triplet syn-2-formylarylnitrene upon UV-irradiation under cryogenic conditions.…”

Section: Heavy-atom Qmtmentioning

confidence: 99%

“…95,96 About a dozen examples of direct spectroscopic observation of carbon-atom QMT occurring under matrix isolation conditions have been reported. 96–100 In recent investigations, we have also discovered a new and distinctive case of a heavy-atom QMT reaction involving the displacement of both nitrogen and oxygen atoms. 101…”

Section: Heavy-atom Qmtmentioning

confidence: 99%

IR-induced and tunneling reactions in cryogenic matrices: the (incomplete) story of a successful endeavor

2022

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“…Both reactants violate Bredt's rule by exhibiting a double bond at the bridgehead of a bicyclic system and thus can overcome the thermodynamic penalty of forming highly reactive species. The ring opening of 13 was recently demonstrated to strongly accelerate in the presence of Lewis acids, offering a proof of concept for the catalysis of tunneling reactions [26] . 4‐Amino‐2 H ‐benzazirine ( 15 a ), on the other hand, constitutes the only known example of a molecule in which two HeavyAT pathways compete at comparable timescales [27] .…”

Section: Ring Openingmentioning

confidence: 99%

Transformations of Strained Three‐Membered Rings a Common, Yet Overlooked, Motif in Heavy‐Atom Tunneling Reactions

Schleif

2022

Chemistry A European J

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Quantum mechanical tunneling has long been recognized as an important phenomenon when considering transformations dominated by a lightweight hydrogen atom. Tunneling of heavier atoms like carbon, initially dismissed as negligible, has seen a quickly increasing number of computationally predicted and/or experimentally confirmed examples over the last decade, thus highlighting its importance for a wide variety of reactions. However, no common structural motif has been pointed out within these seemingly unconnected examples, strongly limiting the predictability of the impact of heavy-atom tunneling on a given reaction. This Concept article will provide this perspective and showcase how the recognition of the formation and cleavage of threemembered rings as common motif can inform the prediction of and research into heavy-atom tunneling reactions.

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Lewis acid catalyzed heavy atom tunneling – the case of 1H-bicyclo[3.1.0]-hexa-3,5-dien-2-one

Abstract: For many thermal reactions, the effects of catalysis or the influence of solvents on reaction rates can be rationalized by simple transition state models. This is not the case for...

Cited by 13 publications

References 35 publications

Solvation Effects on Quantum Tunneling Reactions

Solvation Effects on Quantum Tunneling Reactions

IR-induced and tunneling reactions in cryogenic matrices: the (incomplete) story of a successful endeavor

Transformations of Strained Three‐Membered Rings a Common, Yet Overlooked, Motif in Heavy‐Atom Tunneling Reactions

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