Modulation of Carbenic Reactivity by π-Complexation to Aromatics

Moss, Robert A.; Yan, Shunqi; Krogh‐Jespersen, Karsten

doi:10.1021/ja973649l

Cited by 46 publications

(33 citation statements)

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“…For example, it has been experimentally found that the formation of complexes extends the lifetime of carbenes, 22 changes the selectivity in insertions toward O-H groups, 23 modulates rearrangement products 24 and decreases the reaction constants of addition to olefins or of the ylide formation. 19,25 All of the above mentioned findings were supported by computational calculations 26,27 in which the metastable species were described from proposed 1 : 1 carbene:solvent molecular complexes. In general, the suggested complexes are of p-type and of O-ylidic-type, 20,28,29 in which the carbene carbon interacts with the p system or with the oxygen lone pair of the solvent molecule, respectively.…”

Section: Introductionmentioning

confidence: 62%

Theoretical tools to distinguish O-ylides from O-ylidic complexes in carbene–solvent interactions

Gómez

Restrepo

Hadad

2015

Phys. Chem. Chem. Phys.

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In this paper, we report the geometries and properties of 48 molecular species located on the MP2/6-311++G(d,p) PES of the fluorocarbene-(methanol)3 system. The structures were found by a combination of a stochastic search method, using a modified Metropolis acceptance test, and some hand constructed very symmetrical structures. We use several theoretical descriptors to categorize these species, focusing our attention on the interaction between the carbene carbon and the methanol oxygen, CcO, because this is the key interaction in the formation of O-ylides, ether products, and O-ylidic solvation complexes. These descriptors include natural charges and natural bond orbitals (NBO), CcO bond orders, CcO distances, energetic stabilities, and properties at bond critical points. Accordingly, the isomers were divided into four groups: ethers, fluorocarbene-methanol O-ylides, O-ylidic carbene-solvent complexes and hydrogen bonded carbene-solvent complexes. We found that the possibility of forming H-bonds among solvent molecules and between the carbene carbon and the hydrogen of the solvent molecule affects the stability, structure and nature of CcO interactions in O-ylides and O-ylidic complexes to the point of generating some diffuse borderlines between these two kinds of species. We determined which set of theoretical tools is suitable to better distinguish between them. Additionally, we clarify the nature of the relevant interactions in these species.

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Section: Introductionmentioning

confidence: 62%

Theoretical tools to distinguish O-ylides from O-ylidic complexes in carbene–solvent interactions

Gómez

Restrepo

Hadad

2015

Phys. Chem. Chem. Phys.

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“…Similarly, the ratio of intramolecular rearrangement to intermolecular addition (to tetramethylethylene) for benzylchlorocarbene ( 5 ), propylchlorocarbene ( 6 ), and cyclopropylchlorocarbene ( 7 ) increased in benzene, relative to iso‐octane . Transient carbene–benzene π‐complexes were suggested to be responsible: benzene extended the lifetimes of the carbenes providing a greater opportunity for rearrangement.…”

Section: Introductionmentioning

confidence: 99%

“…Transient carbene–benzene π‐complexes were suggested to be responsible: benzene extended the lifetimes of the carbenes providing a greater opportunity for rearrangement. Also, the complexed carbene might be less apt to add to an alkene …”

Section: Introductionmentioning

confidence: 99%

Solvation and complexation of carbenes – a perspective

Moss

2011

J of Physical Organic Chem

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Complexes of several carbenes with aryl ethers are documented by laser flash photolysis with UV‐visible spectroscopic detection. The carbenes include methylchlorocarbene, benzylchlorocarbene, phenylchlorocarbene, p‐nitrophenylchlorocarbene, and dichlorocarbene, whereas the complexing ligands are anisole, various methylanisoles, dibenzo‐18‐crown‐6, dibenzofuran, 1,3‐dimethoxybenzene, and 1,3,5‐trimethoxybenzene. The carbene complexes are characterized both by spectroscopy and computation. Complexation retards the additions of the carbenes to olefins. The complexation of phenylchlorocarbene by 1,3,5‐trimethoxybenzene is shown to be an equilibrium process, and the pertinent thermodynamic parameters are obtained by experiment and computed from theory. Copyright © 2011 John Wiley & Sons, Ltd.

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“…[110] With carbenes 56a and 56e, the extent of 1,2-H shift increases, relative to the addition of TME, as the solvent is changed from isooctane to benzene. The behavior of carbene 56f indicates that the effect also extends to ring expansion.…”

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confidence: 98%

“…Therefore, it has been suggested that carbene-benzene complexes may be more robust ''because their continuation to product formation will be energetically less favorable''. [110] …”

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confidence: 99%

Carbene Complexes of Nonmetals

Kirmse

2005

Eur J Org Chem

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Electrophilic carbenes accept a variety of n‐ and π‐donors. The products range from persistent ylides to matrix‐isolated xenon complexes. Ylides can be viewed as carbene complexes if they regenerate carbenes thermally or undergo concerted methylene transfer reactions. According to these definitions, the present review focuses on oxonium and iodonium ylides. Transient π‐complexes appear to be involved in addition reactions of carbenes with arenes (but not with alkenes). Nucleophilic carbenes form adducts with Lewis acids which are, for the most part, stable and have been well characterized structurally. Only recently attention has been directed to reversible systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Modulation of Carbenic Reactivity by π-Complexation to Aromatics

Cited by 46 publications

References 21 publications

Theoretical tools to distinguish O-ylides from O-ylidic complexes in carbene–solvent interactions

Theoretical tools to distinguish O-ylides from O-ylidic complexes in carbene–solvent interactions

Solvation and complexation of carbenes – a perspective

Carbene Complexes of Nonmetals

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