Mechanisms of Copper‐mediated Addition and Substitution Reactions

Mori, Susumu; Nakamura, Eiichi

doi:10.1002/3527600086.ch10

Cited by 40 publications

(24 citation statements)

References 154 publications

(214 reference statements)

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“…The facial selectivity may in part be accounted for by the formation of a transient and reversible metallocyclopropane undergoing oxidative addition/reductive elimination with the α,β-unsaturated system. 21 The effect is to exaggerate steric repulsion at the more congested face and is in line with the Dewar−Chatt−Duncanson model. 22 Following this reasoning, the main sequence of the total synthesis was put in train (Scheme 3).…”

Section: ■ Results and Discussionsupporting

confidence: 64%

“…In the preceding example, we observed a pronounced selectivity in terms of β-chirality, favoring the less hindered face. The facial selectivity may in part be accounted for by the formation of a transient and reversible metallocyclopropane undergoing oxidative addition/reductive elimination with the α,β-unsaturated system . The effect is to exaggerate steric repulsion at the more congested face and is in line with the Dewar–Chatt–Duncanson model .…”

Section: Resultsmentioning

confidence: 84%

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Total Synthesis of (−)-Mucosin and Revision of Structure

et al. 2018

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The first total synthesis of (−)-mucosin ( 6), an unusual marine hydrindane natural product incorporating a prostaglandin-like submotif, has been achieved. As a result of the campaign, three of the four all-carbon stereocenters in the purported structure 1 have been revised. Of particular note is the excellent control over β-chirality in conjugate addition to ester (−)-22 and the facial selectivity in the subsequent protonation of an intermediate silyl ketene acetal.

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Section: ■ Results and Discussionsupporting

confidence: 64%

Section: Resultsmentioning

confidence: 84%

Total Synthesis of (−)-Mucosin and Revision of Structure

et al. 2018

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“…[8] Despite the synthetic importance of this promising catalytic process, as yet relatively few mechanistic studies have been reported on enantioselective copper-catalyzed cycloaddition reactions of dialkylzinc reagents. [9][10][11] No detailed mechanistic or structural study concerning the combination of phosphoramidite ligands with copper salts and dialkylzinc reagents has been published to date, but a mechanism based on the principles proposed for non-catalytic organocuprate addition [12][13][14][15] has been postulated. [4,5] The current mechanistic view is that as a first step a transmetalation between the organometallic compound and the copper species takes place, with experimental evidence from NMR chemical shifts in two cases.…”

Section: Introductionmentioning

confidence: 99%

Influence of Copper Salts, Solvents, and Ligands on the Structures of Precatalytic Phosphoramidite Copper Complexes for Conjugate Addition Reactions

Zhang

Gschwind

2007

Chemistry A European J

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For copper-catalyzed enantioselective conjugate addition reactions of organozinc reagents, the available knowledge about the mechanism and the structures involved is still insufficient to understand in detail the strong influences of solvent, salt, and ligand size, or to enable a rational control of this reaction. Screening with three phosphoramidite ligands and four copper(I) salts using NMR spectroscopy has revealed a binuclear copper complex with mixed trigonal/tetrahedral stereochemistry as the basic structural motif of the ground state of precatalysts with highly stereoselective ligands. Ligands with smaller amine moieties allow higher coordination numbers and higher aggregation levels, leading to reduced ee values. Since the ESI mass spectra of several precatalytic copper halide complexes show a striking correlation with the structures observed in solution, ESI-MS may be used as a fast tool to determine the maximum number of phosphoramidite ligands attached to copper.

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“…Typically, organozinc and Grignard reagents are employed as the terminal alkyl (R – ) source with a wide range of in situ formed copper(I) catalysts using diverse chiral ligands (L), including phosphines, N-heterocyclic carbenes (NHCs), and especially phosphoramidites . The consensus mechanistic view of these 1,4-additions to enones (and related Michael acceptors), catalyzed by “RCuL n ”, is given in Scheme . Rapid reduction by MR (e.g., RMgX, ZnR 2 ) of copper(II) precatalysts means that only catalytic cycles starting from Cu I operate.…”

Section: Introductionmentioning

confidence: 99%

“…Initial π complexes 1 are thought to undergo oxidative addition to σ-alkyl Cu III complexes 2 . The reductive elimination step is thought to be the stereodetermining turnover-limiting step, and this has been proposed to be strongly accelerated by coordination of π-acceptor ligands to the σ-Cu III intermediate, providing enolates 3 . − The organocopper byproduct is then recycled to 1 to restart the catalytic cycle. The role of the bridging ligand (X) is to arrange the hard (M) and soft (Cu I ) Lewis acidic sites to provide dual activation for the Michael acceptor; both halides and pseudohalides have been used in this role.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Analysis of Copper(I)/Feringa-Phosphoramidite Catalyzed AlEt₃ 1,4-Addition to Cyclohex-2-en-1-one

et al. 2017

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ReactIR studies of mixtures of AlEt3 (A) and cyclohex-2-en-1-one (CX) in Et2O indicate immediate formation of the Lewis acid–base complex CX·A at −40 °C (K = 12.0 M–1, ΔG°react = −1.1 kcal mol–1). Copper(I) catalysts, derived from precatalytic Cu(OAc)2 (up to 5 mol %) and (R,S,S)-P(binaphtholate){N(CHMePh)2} (Feringa’s ligand (L), up to 5 mol %) convert CX·A (0.04–0.3 M) into its 1,4-addition product enolate (E) within 2000 s at −40 °C. Kinetic studies (ReactIR and chiral GC) of CX·A, CX, and (R)-3-ethylcyclohexanone (P, the H+ quenching product of enolate E) show that the true catalyst is formed in the first 300 s and this subsequently provides P in 82% ee. This true catalyst converts CX·A to E with the rate law [Cu]1.5[L]0.66[CX·A]1 when [L]/[Cu] ≤ 3.5. Above this ligand ratio inhibition by added ligand with order [L]−2.5 is observed. A rate-determining step (rds) of Cu3 L 2(CX·A)2 stoichiometry is shown to be most consistent with the rate law. The presence of the enolate in the active catalyst best accounts for the reaction’s induction period and molecularity as [E] ≡ [CX·A]. Catalysis proceeds through a “shuttling mechanism” between two C 2 symmetry related ground state intermediates. Each turnover consumes 1 equiv of CX·A, expels one molecule of E, and forms the new Cu–Et bond needed for the next cycle. The observed ligand (L) inhibition and a nonlinear ligand L ee effect on the ee of P are well simulated by the kinetic model. DFT studies (ωB97X-D/SRSC) support coordination of CX·A to the groundstate Cu trimer and its rapid conversion to E.

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Mechanisms of Copper‐mediated Addition and Substitution Reactions

Cited by 40 publications

References 154 publications

Total Synthesis of (−)-Mucosin and Revision of Structure

Total Synthesis of (−)-Mucosin and Revision of Structure

Influence of Copper Salts, Solvents, and Ligands on the Structures of Precatalytic Phosphoramidite Copper Complexes for Conjugate Addition Reactions

Kinetic Analysis of Copper(I)/Feringa-Phosphoramidite Catalyzed AlEt₃ 1,4-Addition to Cyclohex-2-en-1-one

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Mechanisms of Copper‐mediated Addition and Substitution Reactions

Cited by 40 publications

References 154 publications

Total Synthesis of (−)-Mucosin and Revision of Structure

Total Synthesis of (−)-Mucosin and Revision of Structure

Influence of Copper Salts, Solvents, and Ligands on the Structures of Precatalytic Phosphoramidite Copper Complexes for Conjugate Addition Reactions

Kinetic Analysis of Copper(I)/Feringa-Phosphoramidite Catalyzed AlEt3 1,4-Addition to Cyclohex-2-en-1-one

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Kinetic Analysis of Copper(I)/Feringa-Phosphoramidite Catalyzed AlEt₃ 1,4-Addition to Cyclohex-2-en-1-one