Role of agostic interaction in .beta.-elimination of palladium and nickel complexes. An ab initio MO study

Koga, Nobuaki; Obara, Shigeru; Kitaura, Kazuo; Morokuma, Keiji

doi:10.1021/ja00310a059

Cited by 148 publications

(88 citation statements)

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“…65,66,67,68,69 Furthermore, in all cases racemic alkyl electrophiles were employed, yet the products are produced in high enantiomeric excess. Recent mechanistic studies have elucidated the operating catalytic cycle (Scheme 6).…”

Section: Stereoablative Transformationsmentioning

confidence: 99%

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

et al. 2017

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An important subset of asymmetric synthesis is dynamic kinetic resolution, dynamic kinetic asymmetric processes and stereoablative transformations. Initially, only enzymes were known to catalyze dynamic kinetic processes but recently various synthetic catalysts have been developed. This review summarizes major advances in non-enzymatic, transition metal promoted dynamic asymmetric transformations reported between 2005 and 2015.

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Section: Stereoablative Transformationsmentioning

confidence: 99%

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

et al. 2017

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“…This exquisite transselectivity could be explained by the fact that the hydrogen atom highlighted by agray disc in A (Figure 1) is the only one in this conformer of the five-membered metallacycle which is correctly positioned to develop an agostic interaction with the metal prior to b-H elimination. [5,16] Hence,p lacing the cis isomer of 10 a under the reaction conditions led to only limited isomerization into its trans isomer (Z/E = 4.7:1). Monosubstituted 9i could be converted into 10 i,a lbeit with decomposition owing to the instability of both 9i and 10 i, even in the absence of catalyst.…”

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confidence: 96%

Isomerization of Olefins Triggered by Rhodium‐Catalyzed CH Bond Activation: Control of Endocyclic β‐Hydrogen Elimination

Yip

Aïssa

2015

Angew Chem Int Ed

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Five-membered metallacycles are typically reluctant to undergo endocyclic β-hydrogen elimination. The rhodium-catalyzed isomerization of 4-pentenals into 3-pentenals occurs through this elementary step and cleavage of two C–H bonds, as supported by deuterium-labeling studies. The reaction proceeds without decarbonylation, leads to trans olefins exclusively, and tolerates other olefins normally prone to isomerization. Endocyclic β-hydrogen elimination can also be controlled in an enantiodivergent reaction on a racemic mixture.

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“…What is the nature of this interaction? Is it only electrostatic or are there other effects present such as agostic [12,17] interactions, whereby electron density in C--H bonds is donated into low-lying empty Li orbitals. We consider this further by examining with the help of STO-3G calculations the lowest unoccupied orbitals of Li 6+ which are primarily combinations of 2s orbitals.…”

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confidence: 99%

A theoretical study of some possible alkyllithium hexamers

1996

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Using ab initio SCF calculations we optimized three possible structures of hexameric methyllithium each having a near octahedral geometry of lithium atoms with capping methyl groups. The isomer in which the vacant faces of the octahedron are trans to each other is the most stable. The alternative structure with the vacant faces in apical contact is 8.8 kcal/mol (6-31G*//4-31G) higher in energy while the edge contact isomer is 26.3 kcal/mol more energetic than the trans structure. The methyl groups were found not to be faced centered. These results are rationalized electrostatically.KEY WORDS: Alkyllithiums; methyllithium; electrostatic interaction; agostic interaction; lithium hydride.Experimental studies have shown that alkyllithiums exist as oligomers in solid state [1-6], gas phase In this paper, we study hexameric methyllithium using theoretical methods. Experimental work [3][4][5][6] suggests that hexameric alkyllithiums have octahedral or near-octahedral geometry. Octahedral hexamers present several points of interest by virtue of their geometry: six lithium atoms with six alkyl groups capping six faces of the octahedron. Because only six of the eight faces are capped there exist three possible structural isomers--trans, in which the two unoccupied faces have no contact, apical in which there is apical contact, and one,

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Role of agostic interaction in .beta.-elimination of palladium and nickel complexes. An ab initio MO study

Cited by 148 publications

References 0 publications

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

Isomerization of Olefins Triggered by Rhodium‐Catalyzed CH Bond Activation: Control of Endocyclic β‐Hydrogen Elimination

A theoretical study of some possible alkyllithium hexamers

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