New chiral scandium(III)/bisimine and diol complexes catalyzed asymmetric Diels–Alder reaction

Fukuzawa, Shin‐ichi; Komuro, Yoshitaka; Nakano, Narihito; Obara, Shinya

doi:10.1016/s0040-4039(03)00674-9

Cited by 26 publications

(15 citation statements)

References 23 publications

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“…In the case of the reaction with N-benzylidene-benzenesulfonamide and N-benzylidene-4-nitrosulfonamide (entries 13-15) the enantioselectivities are comparable with the reaction of N-tosylaldimines. However, electron donating substituents on the aromatic ring of indole gave good to excellent yields and enantioselectivities (entries 16,17). A similar result was obtained in the case of an electron withdrawing group (ee, 89%; entry 16), but when using the N-methyl substituted indole only a trace amount of product was obtained (entry 19).…”

Section: Resultssupporting

confidence: 52%

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Asymmetric Friedel–Crafts addition of indoles to N-sulfonyl aldimines catalyzed by Cu(ii) chiral amino alcohol based Schiff base complexes

Kumari

Bera

Khan

et al. 2014

Catal. Sci. Technol.

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Recyclable copper(II) chiral amino alcohol based Schiff base complexes smoothly catalysed the Friedel-Crafts alkylation of indole with aryl aldimine in good yields (98%) and with enantioselectivities up to 97%. The effects of ligand structure, solvent, metal source and temperature on the reaction were also studied. The catalytic system worked very well several times retaining its performance. To understand the mechanism of the catalytic Friedel-Crafts addition reaction, a kinetic investigation was carried out with different concentrations of the catalyst Cu(II)-L 2 , indole and N-(3-nitrobenzylidene)-4-methylbenzene sulfonamide as a model substrate. The Friedel-Crafts alkylation reaction of N-(3-nitrobenzylidene)-4-methylbenzene sulfonamide was first order with respect to the concentration of the catalyst and the nucleophile but did not depend on the initial concentration of the substrate (aryl aldimine). An appropriate mechanism of the Friedel-Crafts alkylation reaction is proposed.

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Section: Resultssupporting

confidence: 52%

“…Chiral Schiff base ligands L 1 -L 4 were prepared 17,18 by the condensation of aromatic bis-aldehyde with different chiral amino alcohols (Fig. 1) and characterised by various physicochemical techniques.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Friedel–Crafts addition of indoles to N-sulfonyl aldimines catalyzed by Cu(ii) chiral amino alcohol based Schiff base complexes

Kumari

Bera

Khan

et al. 2014

Catal. Sci. Technol.

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“…Under the ternary catalytic system, the ligand/metal ratio was reduced to 1/1 from 2/1 to conserve 3 (entry 7 vs 9). In addition, the ternary catalytic system was reproducible, affording a comparable reaction outcome in three runs (entry 9) . The structure of amine significantly impacted enantioselectivity (entries 0, 2−8), likely because amines would be held in near proximity of the La coordination sphere and perturb the transition state of the reaction.…”

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confidence: 99%

An Improved Lanthanum Catalyst System for Asymmetric Amination: Toward a Practical Asymmetric Synthesis of AS-3201 (Ranirestat)

2008

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A catalytic asymmetric amination with a lanthanum/amide complex was significantly improved. The use of lanthanum nitrate hydrate in place of lanthanum triisopropoxide made the process reproducible, scalable, and cost-effective. The development of a ternary catalytic system of La/ligand/amine was a key to high ee and catalytic turnover. A 100 g scale reaction was performed to showcase a practical synthesis of a key intermediate for AS-3201, a highly potent aldose reductase inhibitor.

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“…† The efficiency of Sc(OTf) 3 promoted Lewis acid catalysis is well documented by the work of Kobayashi 13. Note that Fukuzawa et al used mixtures of Sc(OTf) 3 and chiral H 2 SALEN as promising catalyst precursors in asymmetric Diels-Alder reactions 14. …”

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confidence: 99%

Synthesis and structural characterization of scandium SALEN complexes

et al. 2006

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A series of heteroleptic scandium SALEN complexes, [(SALEN)Sc(mu-Cl)]2 and (SALEN)Sc[N(SiHMe2)2] is obtained via amine elimination reactions using [Sc(N(i)Pr2)2(mu-Cl)(THF)]2 and Sc[N(SiHMe2)2]3(THF) as metal precursors, respectively. H(2)SALEN ligand precursors comprising H2Salen [(1,2-ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salpren [(2,2-dimethylpropanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salcyc [(1R,2R)-(-)-1,2-cyclohexanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] and H2Salphen [((1S,2S)-(-)-1,2-diphenylethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] are selected according to solubility and ligand backbone variation ("=N-(R)-N=" bite angle) criteria. Consideration is given to the feasibility of [Cl --> NR2] and [N(SiHMe2)2--> OSiR3] secondary ligand exchange reactions. X-ray crystal structure analyses of donor-free (Salpren)Sc(N(i)Pr2), (R,R)-(Salcyc)Sc[N(SiHMe2)2], (Salen)Sc(OSi(t)BuPh2) and (Salphen)Sc(OSiH(t)Bu2) reveal (i) a very short Sc-N bond distance of 2.000(3) A, (ii) weak beta(Si-H)(amido)-Sc agostic interactions and (iii) an exclusive intramolecularly tetradentate and intrinsically bent coordination mode of the SALEN ligands with angle(Ph,Ph) dihedral angles and Sc-[N(2)O(2)] distances in the 124.27(9)-127.7(3) degrees and 0.638(1)-0.688(1) A range, respectively.

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New chiral scandium(III)/bisimine and diol complexes catalyzed asymmetric Diels–Alder reaction

Cited by 26 publications

References 23 publications

Asymmetric Friedel–Crafts addition of indoles to N-sulfonyl aldimines catalyzed by Cu(ii) chiral amino alcohol based Schiff base complexes

Asymmetric Friedel–Crafts addition of indoles to N-sulfonyl aldimines catalyzed by Cu(ii) chiral amino alcohol based Schiff base complexes

An Improved Lanthanum Catalyst System for Asymmetric Amination: Toward a Practical Asymmetric Synthesis of AS-3201 (Ranirestat)

Synthesis and structural characterization of scandium SALEN complexes

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