Theoretical Study of the Reaction of Allylsilanes with Carbonyl Compounds

Omoto, Kiyoyuki; Sawada, Yoshito; Fujimoto, Hiroshi

doi:10.1021/ja953090u

Cited by 28 publications

(17 citation statements)

References 57 publications

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“…The reaction is shown to take place via a transition state having a chair form six-membered ring. The B−O and B−C bonds have been calculated to be 1.616 and 1.673 Å, respectively, at the MP2/6-31G** level of the theory, which are seen to be considerably shorter than the Si−O and Si−C bonds, 1.997 and 2.044 Å, respectively, in the reaction of allylsilacyclobutane with formaldehyde . The transition state is more compact in the reaction of boronate.…”

Section: Resultsmentioning

confidence: 94%

Theoretical Study of the Effects of Structure and Substituents on Reactivity in Allylboration

Omoto

Fujimoto

1998

J. Org. Chem.

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To clarify the structural factors controlling the reactivity of allylboron derivatives in allylboration, we have carried out a theoretical analysis by applying the ab initio MO method. Electrophilicity of the boron center in several types of allylboron models has been estimated by projecting out the unoccupied reactive orbital that has the maximum amplitude on a boron p-type atomic orbital chosen specifically. Two important factors, the electron-accepting level and vacancy of the orbital of the reaction site, have been included for the purpose of comparing the relative reactivity of those molecules. The theoretically estimated electrophilicity of the boron center is mostly in agreement with experimental observations for allylborons with different chiral auxiliary structures, indicating that electron delocalization from the oxygen of an attacking aldehyde to the boron of an allylboron reagent dominates the reaction. The activation energies of the reaction have been calculated by locating the complex and the transition states on the potential surfaces to compare with the experimental results and the theoretically estimated electrophilicity.

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Section: Resultsmentioning

confidence: 94%

Theoretical Study of the Effects of Structure and Substituents on Reactivity in Allylboration

Omoto

Fujimoto

1998

J. Org. Chem.

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“…On the other hand, in the inversion pathway, pseudorotation is involved during formation of TS inv via the initial axial attack of the oxaallyl oxygen on silicon (inversion path in Figure ), with the oxaallyl carbon leaving from an equatorial position. Although elimination of an axial ligand from a pentacoordinate silicon intermediate is usually favored over the elimination of an equatorial ligand, , several reactions are known theoretically to proceed via the elimination of an equatorial ligand 3 Schematic representation of the structural change along the intrinsic reaction coordinate. …”

Section: Resultsmentioning

confidence: 99%

A Theoretical Study of Mechanisms of 1,3-Silyl Migration in Formylmethylsilane and Related Migrations. Comparison with Allylsilane

Takahashi

Kira

1999

J. Am. Chem. Soc.

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Two concerted pathways leading to retention and inversion of stereochemistry at the migrating silicon center were found for the isomerization of formylmethylsilane to siloxyethene by ab initio molecular orbital calculations. The activation energy for the retention pathway has been calculated at the MP2/6-311++G(3df, 2p)//MP2/6-311++G** level to be 32 kcal/mol, which is ca. 30 kcal/mol smaller than that for the inversion pathway. The predicted exclusive retention stereochemistry and the calculated activation energy are in good agreement with the experimental results for a silylmethyl ketone with an optical active silyl group. Remarkable differences in the retention transition structures between the 1,3-silyl migrations in formylmethylsilane and the 1,3-silyl migrations in allylsilane are revealed by detailed analysis of geometries, natural bond orbitals, and the Laplacian (∇2ρ) of the wave function. The retention 1,3-silyl migration in formylmethylsilane is best described as an intramolecular nucleophilic substitution at silicon, while the corresponding 1,3-silyl migration in allylsilane is as an electrocyclic sigmatropic rearrangement controlled by subjacent orbital interactions. For related 1,3-migrations in HC(O)CH2MH3 (M = C, Si, Ge, Sn), the E a values for the retention pathway are much lower than the inversion pathway and they decrease in the following order: M = C ≫ Si > Ge > Sn (as expected from the relative stability of the pentacoordinate structure among the metals). A facile 1,3-migration from carbon to nitrogen in iminomethylsilane is predicted to occur with retention stereochemistry via an intramolecular nucleophilic substitution, which is similar to that in formylmethylsilane.

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“…Hunig's base (0.13 mL, 0.75 mmol, 2.5 equiv) was added followed by tert-butyl(chloro)diphenylsilane (165 mg, 0.19 mmol, 2.0 equiv) and the solution was allowed to warm to room temperature with stirring for 15 h. The reaction was quenched with H 2 O (10 mL) and extracted with DCM (10 mL × 3). Purification by chromatography on silica (20:1 to 10:1 (7). The general procedure was followed with 6 (0.10 g, 0.49 mmol).…”

Section: ■ Conclusionmentioning

confidence: 99%

“…In particular, we found that reagents of type 1 are capable of remarkably chemoselective nucleophilic additions to various hydroxyl-substituted carbonyls. This chemoselectivity is thought to arise from a mechanism involving first exchange of the alkoxy substituent on silicon with a substrate hydroxyl, followed by intramolecular allylsilylation of a nearby carbonyl activated by the Lewis acidic silacyclobutane. − …”

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Chemoselective Carbonyl Allylations with Alkoxyallylsiletanes

et al. 2019

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Alkoxyallylsiletanes are capable of highly chemo-and diastereoselective carbonyl allylsilylations. Reactive substrates include salicylaldehydes and glyoxylic acids. Chemoselectivity in these reactions is thought to arise from a mechanism involving first exchange of the alkyoxy group on silicon with a substrate hydroxyl followed by activation of a nearby carbonyl by the Lewis acidic siletane and intramolecular allylation. In this way, substrates containing multiple reactive carbonyl groups (e.g. dialdehyde or triketone) can be selectively monoallylated, even overcoming inherent electrophilicity bias (e.g. nucleophilic addition to a ketone in the presence of an aldehyde).

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Theoretical Study of the Reaction of Allylsilanes with Carbonyl Compounds

Cited by 28 publications

References 57 publications

Theoretical Study of the Effects of Structure and Substituents on Reactivity in Allylboration

Theoretical Study of the Effects of Structure and Substituents on Reactivity in Allylboration

A Theoretical Study of Mechanisms of 1,3-Silyl Migration in Formylmethylsilane and Related Migrations. Comparison with Allylsilane

Chemoselective Carbonyl Allylations with Alkoxyallylsiletanes

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