Asymmetric catalysts

Wills, Martin; Tye, Heather

doi:10.1039/a906654f

Cited by 21 publications

(12 citation statements)

References 420 publications

(252 reference statements)

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“…In recent years, optically active bidentate donor species containing sp 2 -hybridized nitrogen atoms have attracted much attention as ligands for transition-metal-catalyzed asymmetric transformations . For example, enantiomerically pure C 2 -symmetric bis-oxazolines have afforded high levels of enantioselectivity in a number of asymmetric processes such as the Diels−Alder2a or the Mukaiayma 2b reactions and in two important palladium-catalyzed processes, namely allylic alkylation 2c-e and alternating copolymerization of substituted styrenes with CO 2f…”

Section: Introductionmentioning

confidence: 99%

Palladium(II) Complexes of Chiral 1,2-Diiminophosphoranes: Synthesis, Structural Characterization, and Catalytic Activity for the Allylic Alkylation

et al. 2000

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Chiral 1,2-bis[tris(dimethylamino)phosphinimino]cyclohexane (7a, 80% yield), 1,2-bis[tris-(dimethylamino)phosphinimino]-1,2-diphenylethane (7b, 74% yield), 1,2-bis[triphenoxyphosphinimino]cyclohexane (9a, 85% yield), and 1,2-bis[triphenoxyphosphinimino]-1,2-diphenylethane (9b, 70% yield) have been prepared using (1R,2R)-1,2-diaminocyclohexane or (1R,2R)-1,2-diphenylethylenediamine and the corresponding phosphine dibromide derivatives (the Kirsanov route). 1,2-Bis[triphenylphosphinimino]cyclohexane (2), 1,2-bis[triphenylphosphinimino]-1,2-diphenylethane (3), and 1,2-diiminophosphoranes 7b and 9b reacted with [Pd(η 3 -C 3 H 5 )Cl] 2 in the presence of a silver salt in CH 2 Cl 2 at room temperature to afford the cationic complexes 10 (81% yield), 11 (84% yields), 15 (78% yield), and 16 (74% yield), respectively. According to the same general procedure, palladium complexes [(η 3 -PhCHCHCHPh)(2)Pd]TfO (13, 88% yield) and [(η 3 -PhCHCHCHPh)(3)Pd]TfO (14, 86% yield) have been prepared. Single-crystal X-ray diffraction studies of derivatives 10, 11, and 13 have been carried out. They revealed that C 2 symmetry was retained for derivative 3 upon coordination, but lost for 2 in the coordination sphere of the metal. 13 C NMR chemical shifts for the terminal C atoms of the allyl moiety of these complexes indicate that the donor ability of 1,2-diiminophosphoranes varies with the nature of the P-substituents and is comparable to that of other sp 2 -hybridized nitrogen ligands. 1,2-Diiminophosphoranes were evaluated as ligands for the Pd-catalyzed enantioselective allylic substitution reaction of rac-1,3diphenylprop-2-enyl acetate with the anion of dimethyl malonate. Ligands 3 and 7a,b induce good catalytic activities compared with other N,N-ligands but moderate ee's (10-77%) at 36 °C. Higher ee's (85%) were obtained at room temperature with ligand 3 but at the expense of the catalytic activity. This study revealed that 1,2-diimonophosphoranes are able to stabilize Pd(0) species during a catalytic process and to induce notable levels of enantioselectivity.

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Section: Introductionmentioning

confidence: 99%

Palladium(II) Complexes of Chiral 1,2-Diiminophosphoranes: Synthesis, Structural Characterization, and Catalytic Activity for the Allylic Alkylation

et al. 2000

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“…A vast amount of chiral ligands for catalysts have been designed. 1 We have developed methods for regioselective introduction of various substituents in substituted N-hydroxy azoles. 2 Combining these two aspects led us to the design of new potential ligands, based on substituted N-hydroxyazoles.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of a new analogue of BINOL based on a homodimer of substituted 1-hydroxypyrazole

Rist

Begtrup

2001

J. Chem. Soc., Perkin Trans. 1

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“…In typical palladium-catalyzed intermolecular asymmetric allylations, the enantioselectivity is set by the attack of the nucleophile on one of two different carbons of a palladium allyl complex (4). [11][12][13][14][15][16][17][18] In this reaction, the asymmetric induction takes place during the formation of the allylic complex when one of the two enantiotopic carbamates is lost to form the intermediate palladium complex (7 vs 7′).…”

mentioning

confidence: 99%

Parallel Approach to Selective Catalysts for Palladium-Catalyzed Desymmetrization of 2,4-Cyclopentenediol

2003

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Asymmetric catalysts

Cited by 21 publications

References 420 publications

Palladium(II) Complexes of Chiral 1,2-Diiminophosphoranes: Synthesis, Structural Characterization, and Catalytic Activity for the Allylic Alkylation

Palladium(II) Complexes of Chiral 1,2-Diiminophosphoranes: Synthesis, Structural Characterization, and Catalytic Activity for the Allylic Alkylation

Synthesis of a new analogue of BINOL based on a homodimer of substituted 1-hydroxypyrazole

Parallel Approach to Selective Catalysts for Palladium-Catalyzed Desymmetrization of 2,4-Cyclopentenediol

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