Alkylations of Nonstabilized Carbanions

Klunder, Janice M.; Posner, Gary H.

doi:10.1016/b978-0-08-052349-1.00062-7

Cited by 28 publications

(6 citation statements)

References 343 publications

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“…Its importance and the number of applications are simply impressive, ranging from the simple nucleophilic substitution to the Heck reaction . Among the common methodologies known for C−X bond activation, the use of Lewis acids such as AlCl 3 , Ag + , Cu + , and Tl + ions are popular and convenient …”

Section: Introductionmentioning

confidence: 99%

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

et al. 2003

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The stoichiometric and catalytic activations of alkyl halides and acid chlorides by the unsatured Pd(3)(dppm)(3)(CO)(2+) cluster (Pd(3)(2+)) are investigated in detail. A series of alkyl halides (R-X; R = t-Bu, Et, Pr, Bu, allyl; X = Cl, Br, I) react slowly with Pd(3)(2+) to form the corresponding Pd(3)(X)(+) adduct and "R(+)". This activation can proceed much faster if it is electrochemically induced via the formation of the paramagnetic species Pd(3)(+). The latter is the first confidently identified paramagnetic Pd cluster. The kinetic constants extracted from the evolution of the UV-vis spectra for the thermal activation, as well as the amount of electricity to bring the activation to completion for the electrochemically induced reactions, correlate the relative C-X bond strength and the steric factors. The highly reactive "R(+)" species has been trapped using phenol to afford the corresponding ether. On the other hand, the acid chlorides react rapidly with Pd(3)(2+) where no induction is necessary. The analysis of the cyclic voltammograms (CV) establishes that a dissociative mechanism operates (RCOCl --> RCO(+) + Cl(-); R = t-Bu, Ph) prior to Cl(-) scavenging by the Pd(3)(2+) species. For the other acid chlorides (R = n-C(6)H(13), Me(2)CH, Et, Me, Pr), a second associative process (Pd(3)(2+) + RCOCl --> Pd(3)(2+.....)Cl(CO)(R)) is seen. Addition of Cu(NCMe)(4)(+) or Ag(+) leads to the abstraction of Cl(-) from Pd(3)(Cl)(+) to form Pd(3)(2+) and the insoluble MCl materials (M = Cu, Ag) allowing to regenerate the starting unsaturated cluster, where the precipitation of MX drives the reaction. By using a copper anode, the quasi-quantitative catalytic generation of the acylium ion ("RCO(+)") operates cleanly and rapidly. The trapping of "RCO(+)" with PF(6)(-) or BF(4)(-) leads to the corresponding acid fluorides and, with an alcohol (R'OH), to the corresponding ester catalytically, under mild conditions. Attempts were made to trap the key intermediates "Pd(3)(Cl)(+)...M(+)" (M(+) = Cu(+), Ag(+)), which was successfully performed for Pd(3)(ClAg)(2+), as characterized by (31)P NMR, IR, and FAB mass spectrometry. During the course of this investigation, the rare case of PF(6)(-) hydrolysis has been observed, where the product PF(2)O(2)(-) anion is observed in the complex Pd(3)(PF(2)O(2))(+), where the substrate is well-located inside the cavity formed by the dppm-Ph groups above the unsatured face of the Pd(3)(2+) center. This work shows that Pd(3)(2+) is a stronger Lewis acid in CH(2)Cl(2) and THF than AlCl(3), Ag(+), Cu(+), and Tl(+).

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Section: Introductionmentioning

confidence: 99%

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

et al. 2003

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“…The S N 2 substitution reaction of an organocopper(I) reagent with an alkyl halide and related electrophiles provides uniquely important synthetic methodology for C−C bond formation between a nonstabilized carbanion and a sp 3 electrophilic carbon center . Organocopper(I) reagent is the oldest and still the only reagent of general utility for this transformation.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of S_N2 Alkylation Reactions of Lithium Organocuprate Clusters with Alkyl Halides and Epoxides. Solvent Effects, BF₃ Effects, and Trans-Diaxial Epoxide Opening

2000

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The B3LYP density functional studies on the mechanism of the SN2-substitution reaction of methyl halides and epoxides with lithium organocuprates(I), (CH3)2CuLi·LiCl and [(CH3)2CuLi]2, revealed the energetics and the geometries of important transition states and intermediates along the reaction pathway. In the absence of solvent coordination on the copper atom, the reaction takes place in a single step through rate determining cleavage of the C−X bond (X = leaving group) involving nucleophilic participation of the CH3−Cu bond composed of the copper 3d z 2 orbital and carbon 2s+2p orbitals. Consideration of solvent polarity and coordination of an explicit (CH3)2O molecule to a lithium atom in the cuprate cluster lowers the activation energy to <20 kcal/mol, which is a reasonable value for the reaction taking place below 0 °C. Solvation of the copper atom does not change much the geometry or the energy of the transition state, but modifies the pathway afterward. The origin of the “trans-diaxial opening of cyclohexene oxide” has been ascribed to the inverted stereochemistry of the electrophilic carbon atom in the rate-determining step of the reaction. Coordination of BF3 lowers the activation energy of the nucleophilic ring opening of epoxide as much as to 9.2 kcal/mol. The origin of the acceleration of epoxide ring opening by BF3 is attributed to the cooperative activation of borane and lithium atoms on the epoxide oxygen atom.

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“…Reactions of organocopper reagents with alkyl halides and tosylates and allylic substrates have been extensively used in organic synthesis as a powerful method for C−C bond formation . In the early stages of organocopper chemistry, Whitesides et al demonstrated that a reaction of a homocuprate (R 1 2 CuLi) with an alkyl halide (R 2 −X) exclusively gives a cross-coupling product (R 1 −R 2 ). ,3a The failure to observe homocoupling products even from the reaction of (CH 3 ) 2 CuLi with CD 3 I led to the assumption that the T-shaped intermediate A is formed 3b…”

mentioning

confidence: 99%

Unusual Homocoupling in the Reaction of Diorganocuprates with an Allylic Halide

et al. 2006

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The reactions of dialkyl-and diarylcuprates (R 2 CuM; M ) Li, MgBr) with perfluoroallyl iodide were found to giVe the homocoupling products R-R as the only product of C-C bond formation. Density functional calculations reVealed that the perfluoroallyl ligand, being strongly electron-withdrawing and less Lewis basic, significantly changes the electronic properties of the allylcopper(III) intermediate and acts as a spectator ligand in the reductiVe elimination.

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Alkylations of Nonstabilized Carbanions

Cited by 28 publications

References 343 publications

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

Mechanism of S_N2 Alkylation Reactions of Lithium Organocuprate Clusters with Alkyl Halides and Epoxides. Solvent Effects, BF₃ Effects, and Trans-Diaxial Epoxide Opening

Unusual Homocoupling in the Reaction of Diorganocuprates with an Allylic Halide

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Alkylations of Nonstabilized Carbanions

Cited by 28 publications

References 343 publications

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd3(dppm)3(CO)2+Cluster and Its Catalytic Applications

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd3(dppm)3(CO)2+Cluster and Its Catalytic Applications

Mechanism of SN2 Alkylation Reactions of Lithium Organocuprate Clusters with Alkyl Halides and Epoxides. Solvent Effects, BF3 Effects, and Trans-Diaxial Epoxide Opening

Unusual Homocoupling in the Reaction of Diorganocuprates with an Allylic Halide

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Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

Thermal and Electrochemical C−X Activation (X = Cl, Br, I) by the Strong Lewis Acid Pd₃(dppm)₃(CO)²⁺Cluster and Its Catalytic Applications

Mechanism of S_N2 Alkylation Reactions of Lithium Organocuprate Clusters with Alkyl Halides and Epoxides. Solvent Effects, BF₃ Effects, and Trans-Diaxial Epoxide Opening