A new C2-symmetric azolium compound for Cu-catalyzed asymmetric conjugate addition of R2Zn to cyclic enone

Harano, Ayako; Sakaguchi, Satoshi

doi:10.1016/j.jorganchem.2010.07.038

Cited by 26 publications

(8 citation statements)

References 79 publications

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“…1 H and 13 C NMR data are identical to those described in the literature11 HRMS (FAB + ): calculated for C 17 H 18 N 3 O 2 [M+H] + , m/z 296.1399; found for [M+H] + , m/z 296.1413.4.2.5. (S)-N-(2-Hydroxy-1-phenylethyl)-2-(2H-benzo[d]-[1,2,3] triazol-2-yl)acetamide 1e (125 mg, 45%) as a white solid, mp 202-203°C, [a] D = +128.0 (c 3.0, DMSO).…”

supporting

confidence: 64%

Synthesis of β-hydroxyacetamides from unactivated ethyl acetates under base-free conditions and microwave irradiation

Hernández-Fernández

Sanchez‐Lara

Ordóñez

et al. 2015

Tetrahedron: Asymmetry

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supporting

confidence: 64%

Synthesis of β-hydroxyacetamides from unactivated ethyl acetates under base-free conditions and microwave irradiation

Hernández-Fernández

Sanchez‐Lara

Ordóñez

et al. 2015

Tetrahedron: Asymmetry

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“…A reversal of enantioselectivity was observed by Sakaguchi and co-workers in the copper-catalyzed conjugate addition of alkylzincs to cycloalkenones using the same carbene derived from the chiral ligand 542 . − The addition of diethyl or di- n -butylzinc to cyclic enones catalyzed by copper complexes of the carbene derived from the azolium salt 542a gave adducts ( S )- 543 in the case Cu(OTf) 2 with ee up to 84% (Scheme ). However, changing the copper salt by Cu(acac) 2 gave the corresponding enantiomers ( R )- 543 with ee up to 82% .…”

Section: Stereodivergence In Cyclic Systemsmentioning

confidence: 99%

Stereodivergent Catalysis

2018

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This review covers diastereo- and enantiodivergent catalyzed reactions in acyclic and cyclic systems using metal complexes or organocatalysts. Among them, nucleophilic addition to carbon-carbon and carbon-nitrogen double bonds, α-functionalization of carbonyl compounds, allylic substitutions, and ring opening of oxiranes and aziridines are considered. The diastereodivergent synthesis of alkenes from alkynes is also included. Finally, stereodivergent intramolecular and intermolecular cycloadditions and other cyclizations are also reported.

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“…We have previously demonstrated that a C 2 ‐symmetric bis(hydroxy amide)‐functionalized benzimidazolium salt efficiently performs a copper‐catalyzed ACA addition of R 2 Zn to cyclic enones with up to 96 % ee 13. Therefore we designed and synthesized a similar bis(ester amide)‐functionalized benzimidazolium salt 36 from L ‐serine methyl ester.…”

Section: Resultsmentioning

confidence: 99%

Functionalized N‐Heterocyclic Carbene Ligands for Dual Enantioselective Control in the Cu‐Catalyzed Conjugate Addition of Dialkylzinc Compounds to Acyclic Enones

et al. 2012

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A series of highly tunable, functionalized azolium compounds have been synthesized from chiral α‐amino acid derivatives such as β‐amino alcohols or α‐amino esters. The combination of a Cu salt and a chiral azolium efficiently facilitated the asymmetric conjugate addition (ACA) reactions of acyclic enones with dialkylzinc under ambient conditions without temperature control. Of the (hydroxy amide)‐functionalized azolium ligand precursors, which were derived from β‐amino alcohols, an azolium salt containing a tert‐butyl group as the stereodirecting group was found to be the best choice of ligand. Ligand screening revealed that the use of an azolium salt containing a sterically bulky alkyl substituent such as N‐CHRR′ on the azolium ring led to a marked increase in the enantioselectivity of the ACA reaction. Thus, a new efficient (hydroxy amide)‐functionalized azolium ligand precursor such as 26, which was prepared from 1‐(diphenylmethyl)benzimidazole and (S)‐tert‐leucinol, has been developed. The treatment of benzalacetone (30) with Et2Zn in the presence of catalytic amounts of [Cu(OTf)]2(C6H6) and 26 at room temperature gave the corresponding 1,4‐adduct 31 with excellent enantioselectivity (92 % ee). On the other hand, the enantioselectivity of the ACA reactions of acyclic enones with dialkylzinc was successfully reversed by the use of (ester amide)‐functionalized azolium salts, which were obtained from α‐amino esters. Several functionalized azolium ligand precursors from readily available serine esters have been designed and synthesized. Finally, it was found that 30 could react with Et2Zn under the influence of a bis(hexafluoroacetylacetonato)copper(II) salt and C2‐symmetric azolium salt 36 to afford ent‐31 in almost quantitative yield with 89 % ee. A plausible reaction mechanism for the switching of the stereoselectivity in the ACA reaction by these two functionalized azolium compounds is described.

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A new C2-symmetric azolium compound for Cu-catalyzed asymmetric conjugate addition of R2Zn to cyclic enone

Cited by 26 publications

References 79 publications

Synthesis of β-hydroxyacetamides from unactivated ethyl acetates under base-free conditions and microwave irradiation

Synthesis of β-hydroxyacetamides from unactivated ethyl acetates under base-free conditions and microwave irradiation

Stereodivergent Catalysis

Functionalized N‐Heterocyclic Carbene Ligands for Dual Enantioselective Control in the Cu‐Catalyzed Conjugate Addition of Dialkylzinc Compounds to Acyclic Enones

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