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  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective Catalysis, XIVPart XIII: U. Nagel, H. G. Nedden, Chem Ber. 1997, 130,385-397.Asymmetric Grignard Cross-Coupling Reaction: An Investigation of the Factors Influencing Asymmetric Induction with a New Type of Pyrrolidinephosphane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 535-542 
    Details
    ISSN: 0009-2940
    Keywords: Cross-coupling ; Grignard reactions ; Pyrrolidinephosphanes ; Asymmetric amplification ; Gas chromatography ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An investigation of the asymmetric synthesis of 3-phenyl-1-butene by the Grignard cross-coupling reaction is presented. The reaction is catalysed by nickel complexes of bisphosphane and 3-diphenylphosphanylpyrrolidine-type ligands. A comparison of the results obtained with our P,N monophosphane ligands with those obtained with the most effective known amino acid derived P,N ligands shows a similar enantioselectivity but an inverse sense of optical induction. An X-ray structural analysis of the 1-phenylethyl Grignard compound is reported. Quantitative analysis and the determination of enantiomeric composition of the catalytic samples is accomplished using a novel enantioselective GLC separation. Compared to the popular model reaction that uses a chloride-containing Grignard compound and vinyl bromide as starting compounds, we obtain improved enantioselectivities of P,N monophosphane catalysts by substituting vinyl bromide with vinyl chloride. With two of the new P,N ligands we find a nonlinear dependence of enantioselectivity on the enantiomeric purity of the ligands (asymmetric amplification). Catalytic results subject to such nonlinear effects show a dependence on the ligand to nickel ratio.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300414
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  • 2
    Electronic Resource
    Electronic Resource
    Enantioselective Catalysis, XVPart XIV: Ref. Preparative and Structural Chemistry of Diastereomeric Derivatives of 3-Phosphanylpyrrolidine and Their Palladium(II) Complexes - Asymmetric Grignard Cross-Coupling Reaction (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 989-1006 
    Details
    ISSN: 0009-2940
    Keywords: Cross-Coupling ; Grignard reactions ; Nickel ; Pyrollidinephosphane ; Cooperative effects ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of both diastereomeric derivatives of 3-(diphenylphosphanyl) pyrrolidine with chiral (tetrahydrofuran-2-yl)methyl and [(N-neopentyl)pyrrolidin-2-yl]methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)-1-benzyl-4-(diphenylphosphanyl)-2-(methoxymethyl) pyrrolidine is reported. [3S,P(RS)]-3-(phenylphosphanyl) pyrrolidine, bearing an additional chiral center on phosphorus, is the starting material for the preparation of phosphanes, in which one phenyl group of the PPh2 moiety is substituted by an 2-methoxyphenyl (=An) or 2,4,6-trimethoxyphenyl (=TMP) group. PdI2 complexes of these ligands were separated into diastereomers by chromatography on silica gel columns. The structural chemistry of these novel phosphane diastereomers and their PdI2 complexes is investigated by X-ray crystallography and NMR. At the P,N-coordinated palladium center displacement of an iodide anion is found for P,N,N′ ligands only. In the nickel complex catalysed cross-coupling reaction, yielding 3-phenyl-1-butene, we obtain the highest enantioselectivities in the case of simple 1-alkyl-3-(diphenylphosphanyl)pyrrolidine ligands. The enantioselectivity obtained with diastereomeric derivatives, bearing additional ether or amine ligating sites is mainly determined by the chiral center in 3-position of the 3-(phosphanyl) pyrrolidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nickel ratio and by the choice of the vinyl halide used as starting compound. The catalytic cycle must contain at least one catalytically active species, bearing more than one β aminoalkylphosphane ligand.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300729
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  • 3
    Electronic Resource
    Electronic Resource
    Metallorganische Lewis-Säuren, XLVIII. Neue Vorläufer metallorganischer, kationischer Lewis-Säuren mit zwei freien Koordinationsstellen: (OC)4Re(OEt2)FBF3 und (OC)2(PPh3)2Ru(FBF3)2 (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 927-932 
    Details
    ISSN: 0009-2940
    Keywords: Lewis acids, organometallic ; 14e- Systems ; Allyl complexes ; Rhenium complexes ; Ruthenium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic Lewis Acids, XLVIII[1]. - New Precursors to Organometallic Cationic Lewis Acids with two Accessible Coordination Sites: (OC)4Re(OEt2)FBF3 and (OC)2 (PPh3)2Ru(FBF3)2The allyl transfer reaction between Re(CO)5- and [(η31-allyl)PdCl]2 complexes leads to (allyl)rhenium complexes (η31-H2CCR1CR2R3) Re(CO)4 (1: R1, R2, R3=H; 2; R2, R3=H, R1=Me; 3: R1, R2=H, R3=Me; 4: R1=H, R2, R3=Me). The 2-methylallyl complex 2 has been characterized by low-temperature X-ray diffraction. Protonation of 1 with HBF4 · OEt2 in CH2Cl2 gives the complex (OC)4Re(OEt2)FBF3 (5), which is a precursor for the 14 e- System “(OC)4Re+”. THF and H2O replace the diethyl ether in 5 to give [(OC)4Re(solvent)2]BF4 (6, 7). The reaction of (OC)2(PPh3)2RuCl2 with AgBF4 yields the complex (OC)2 (PPh3)2Ru(FBF3)2 (8), which can be considered as a precursor for the 14 e- cation “(OC)2 (PPh3)2Ru2+” and reacts with H2O to give [(OC)2 (PPh3)2Ru(F)(H2O)]BF4 (9). Complexes 5-9 are characterized by IR, 1H-, 13C-, 31P-and 19F-NMR spectroscopy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260412
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