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  • Cross-coupling  (2)
  • Molecular modelling  (1)
  • 1
    Digitale Medien
    Digitale Medien
    The Effect of the Bite Angle of Diphosphane Ligands on Activity and Selectivity in Palladium-Catalyzed Cross-Coupling (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 155-157 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Bite angle ; Catalysis ; P ligands ; Palladium ; Cross-coupling ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of the natural bite angle (βn) of diphosphane ligands on catalyst selectivity and activity in the palladium-catalyzed cross-coupling of sec-butyl magnesium chloride with bromobenzene was investigated. The calculated natural bite angles range from 78° for dppe (1,2-bisdiphenylphosphanoethane) to 110° for Xantphos. The natural bite angle of diphosphane ligands has a large effect on catalyst selectivity and activity. Both rate and selectivity of the cross-coupling reaction increase with increasing bite angle and reach a maximum value with DPEphos (βn = 102.7° ). Larger bite angles of the diphosphane ligands result in a decreased selectivity and activity.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    On the Influence of the Bite Angle of Bidentate Phosphane Ligands on theRegioselectivity in Allylic Alkylation (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1237-1241 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Palladium ; Phosphane ligands ; Bite angle ; Allylic alkylation ; Molecular modelling ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The natural bite angle of bidentate phosphane ligands influences the isomer distribution (syn and anti) in (1-methylallyl)(bisphosphane)Pd OTf complexes. It was found (31P- and 1H-NMR studies) that the syn/anti ratio changes from 12 (dppp) to 1.3 (sixantphos). Molecular orbital calculations [PM3(tm) level] indicate that for ligands inducing a large bite angle, the phenyl rings of the ligand embrace the allyl moiety, thus influencing the syn/anti ratio. This bite-angle effect on the syn/anti ratio is transferred to the regioselectivity in stoichiometric allylic alkylation. Ligands inducing large bite angles direct the regioselectivity towards the formation of the branched product 2. Catalytic alkylation of (E)-2-butenyl acetate showed that for ligands with a small bite angle the regioselectivity of the catalytic and stoichiometric alkylation are in good agreement. This correspondence is worse for ligands with a larger bite angle, which is rationalised in terms of the relative rates of syn/anti isomerisation and alkylation. The ligand with the largest bite angle (sixantphos) gives the most active catalytic species.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Synthesis of 5-Substituted Resorcinol Derivatives via Cross-Coupling Reactions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 359-364 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Resorcinols ; Cross-coupling ; Demethylation ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Suzuki and Stille cross-coupling reactions were utilized in the synthesis of 5-substituted 1,3-dimethoxybenzene and 5-substituted resorcinol derivatives. The substituted resorcinol derivatives were obtained in only three steps from inexpensive reagents. 1,3-Dimethoxybenzoic acid and 1-chloro-3,5-dimethoxybenzene were transformed into 1-iodo-, 1-bromo-, 1-trimethyltin-3,5-dimethoxybenzene and 3,5-dimethoxyphenyl boronic acid. 5-Allyl-1,3-dimethoxybenzene and 3,5-dimethoxybiphenyl derivatives were obtained via cross coupling reactions under mild conditions. HI, BBr3 and AlI3 were used to demethylate these dimethoxybenzenes into their resorcinol derivatives.
    Materialart: Digitale Medien
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