Tricoordinate Carbanions, Cations, and Radicals

Pale, Patrick; Vogel, P.

doi:10.1016/b0-08-044655-8/00019-2

Cited by 5 publications

(3 citation statements)

References 661 publications

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“…Carbanions are essential reactive intermediates in organic and organometallic chemistry . Their intrinsically low stability has rarely allowed for the isolation and characterization of free carbanions in the solid state, although it appears that the first representative was isolated by Schlenk as early as 1916. , The few free carbanions that have been structurally characterized are stabilized by employing resonance to decrease the charge density on the carbon center and hence reduce its basicity.…”

Section: Introductionmentioning

confidence: 99%

Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks

et al. 2009

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A series of 1,3-bis(2,6-diisopropylphenyl)-5-methyl-1,3-diaza-4,6-diborabenzenes with methyl, phenyl and dimethylamino substituents on the ring boron atoms were prepared using the cyclocondensation reaction between N,N'-bis(2,6-diisopropylphenyl)trimethylsilylformamidine and the appropriately substituted 1,1-bis(organochloroboryl)ethane, followed by deprotonation of the cationic ring intermediate. The planar, heterocyclic benzene analogs could be further deprotonated at the other ring carbon using an additional equivalent of potassium hexamethyldisilazide, to yield organometallic derivatives akin to the potassium phenylide. The potassium cations could be efficiently sequestered in both solution and solid state using 18-crown-6 and the crystallographic analysis of the reaction products revealed the absence of carbanion-cation contacts in the solid state. The transformation of a planar, tricoordinate sp 2 -carbon to a tricoordinate, contact ion-pair carbanion and further to a solvent-separated, free dicoordinate carbanion was investigated using solution NMR and single-crystal X-ray diffraction.The first isolation and characterization of free dicoordinate carbanions in the solid state is supported by 2 a charge distribution analysis, and the relationship between phenylide-type carbanions and Nheterocyclic carbenes is discussed through the prism of the results reported herein.

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Section: Introductionmentioning

confidence: 99%

Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks

et al. 2009

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“…Carbocations are one of the important species in organic chemistry. They have been studied as key reaction intermediates in various reactions over 100 years as written in any textbooks of organic chemistry [1][2][3] and are continuously utilized in organic synthesis. [4] The physical properties of persistent carbocations have also been extensively studied from the interest in conjugation with adjacent cyclic or acyclic πsystems.…”

Section: Introductionmentioning

confidence: 99%

Formation, Chemical and Optical Properties of 1,2,5‐Triphenylpentadienyl Cation Fixed in a Rigid Dibenzobarrelene Skeleton

2022

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1,2,5‐Triphenylpentadienyl cation fused with a dibenzobarrelene skeleton was synthesized. The pentadienyl cation was persistent in the solution and characterized by 1H and 13C NMR spectroscopies. The cation abstracts a hydride from Et2O at the 5‐position to give the 5‐H derivative together with acetaldehyde and ethene. The reaction with H2O provided the 5‐OH derivative and not the 1‐OH precursor. The hydride reduction of the pentadienyl cation with silanes or NaBH4 occurred at the 3‐ and 5‐positions, and the ratio was dependent on the bulkiness of reducing reagents. The cation in dichloromethane exhibited long‐wavelength absorptions at 678, 523, and 443 nm and an emission maximum at 729 nm with the emission quantum yield of 0.175, which are longer and larger than those of the referenced 1,5‐diphenylpentadienyl cation. TD‐DFT calculations show that the absorptions are due to the π‐π* excitations on 1,2,5‐triphenylpentadienyl and dibenzobarrelene benzene rings.

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“…Skeletal rearrangements are powerful processes for generating molecular diversity with atom economy. Numerous transformations, involving neighboring group participation by σ or π bonds, have been reported in the chemistry of bicyclo-[2.2.1] heptanes (norbornanes), and similar participation has also been established for the corresponding 7-azanorbornane skeleton, leading to compounds of high interest via a very short synthetic sequence . In our ongoing work on the use of bicyclic hydrazines as starting material for the synthesis of polyfunctionalized aminocyclopentanes, we recently reported a new route to aminocyclopentitols based on an acid-catalyzed rearrangement of compound 1 (Scheme ) …”

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confidence: 97%

Skeletal Rearrangements in the 2,3-Diazanorbornene Series. A Fast Access to Highly Functionalized Cyclopentanes

2006

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Tricoordinate Carbanions, Cations, and Radicals

Cited by 5 publications

References 661 publications

Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks

Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks

Formation, Chemical and Optical Properties of 1,2,5‐Triphenylpentadienyl Cation Fixed in a Rigid Dibenzobarrelene Skeleton

Skeletal Rearrangements in the 2,3-Diazanorbornene Series. A Fast Access to Highly Functionalized Cyclopentanes

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