Thomas Kauffmann

Hohe aldehydselektivität bei carbonylolefinierungen mit titan- und chrom-reagenzien

Abstract The easily available reagents GCH 2 TiCl 3 (G = (CH 3 ) 3 Si, (CH 3 ) 3 Ge) and (CH 3 ) 3 SiCH 2 CrCl 2 cause carbonylolefination of aldehydes, but not of ketones. In case of the chromium reagent acidic hydrolysis of the products is necessary.

Über verbesserte Ru(II)-hydrierungskatalysatoren mit dreizähnigen cyclopentadienyldiphosphan-liganden (1)

Abstract The novel complexes 4a and b have been synthesized by complexation of Ru(II) with the tridentate ligands Ph 2 P-(CH 2 ) n -P(Ph)-(CH 2 ) 2 -Cp (n = 3,4). 4b, compared with other Ru(II) phosphane complexes, showed superior capacity as hydrogenation catalyst.

Zwei neue reaktionsweisen von alkyl-Mn(II)-verbindungen: 1,4-addition an cyclohex-2-enon(1) und desoxygenierung von oxiranen (1)

Abstract Alkyl Mn(II) compounds react like alkyl Cu(I) compounds specifically or highly selectively with cyclohex-2-enone(1) to give 3-alkylhexanones (Alk  Me, Bu) in medium or good yields. By reacting with oxiranes corresponding alkenes are produced, a reaction not observed so far with alkyl Cu(I) reagents.

Über die aldehydselektivität von alkylkomplexen von scandium, yttrium, lanthan und lanthaniden aldehyd/keton-konkurrenzversuchen

Abstract In-situ prepared alkyl complexes Hal 2 M-Alk (Alk = Me, Bu) of the f-metals Ce, Pr, Nd, Sm, Gd exhibit very low selectivity in competition experiments between heptanal and diethylketone in THF, whereas the selectivity of complexes Hal 2 M-Me (M = Sc, Y, La) is distinctly higher with decreasing tendency in the sequence Sc>Y>La. These and previously reported 1 results led to a general working hypothesis about the reasons of the aldehyde-selectivity of transition metal alkyls.

Selektive kohlenstoff-kohlenstoff-verknüpfungen mit nucleophilen thermolabilen methylcobalt-reagenzien

Abstract Nonstabilized Co(II) methyl derivatives (MeCoCl, Me2Co, Me3CoLi, Me4CoLi2) are readily accessible in solution (THF, Et2O) by reaction of MeLi with CoCl2 at −78°C to −60°C. For checking the transmetallation process the “β-bromostyrene-ketone test” is especially favorable. Characteristic features of the reactivity of the Coreagents: High efficiency in the cross coupling with trans-β-bromostyrene, high aldehyde-vs.-ketone selectivity in Et2O, methylation of 2-cyclohexenone mainly in β-position, the ate-complexes methylate carboxylic esters, but not tertiary carbocyclic amides.

Anwendung nichtstabilisierter eisen(II)-alkyle als hochselektive nucleophile alkylierungsreagenzien

Zusammenfassung Nonstabilized Fe(II) alkyls (RFeCl, R 2 Fe, R 2 FeM, R 4 FeM 2 ; R = Me, n-Bu, M = Li, MgBr) are readily accessible in solution (THF, Et 2 O, CH 2 Cl 2 ) by reaction of MeLi, MeMgBr, n-BuLi or n-BuMgBr, respectively, with FeCl 2 at -78 to -50°C. The needed FeCl 2 can be made by in-situ-reduction with RLi or RMgBr. For checking the transmetallation process the “β-bromostyrene-ketone test” is especially favorable in case of the methyl derivatives. The prepared Fe compounds are alkylating reagents of high selectivity.

Titankomplexe offenkettiger und cyclischer arsanliganden: synthese und katalytische wirkung (1)

The Ti(IV) complexes 1b, 2b, and 6 have been synthesized from new multi-electron ligands. 2b, after reduction with Et2AlCl, dimerizes isoprene mainly to 8c and trimerizes butadiene mainly to ttt-CDT. Ti(IV) compounds of the macrocyclic ligands 7a-c exhibit the same catalytic properties after reduction with Et2AlCl.

Aldehydspezifische und aldehydselektive alkylierungen mit organoniob- und - tantal-reagenzien (1)

Abstract In competition experiments with n-heptanal and diethylketone as substrates the reagents (CH 3 ) 2 M(OiPr) 3 , CH 3 MCl 4 (M = Nb, Ta), and nBuNbCl 4 react exclusively or very selectively with the aldehyde.

Konjugierte addition von alkylderivaten der späten übergangsmetalle Ag, Pd, Rh, Ru, Co und Fe an 2-cyclohexenon☆

Abstract In situ prepared alkyl derivatives of the 4d metals Ag, Rh (Alk = Me, n-Bu), Pd, Ru (Alk = Me) alkylate 2-cyclohexenone ( 1 ) exclusively or preferently in β-position to the keto group. The same was observed by applying Me 2 Fe, Me 3 FeLi or the hetero-ate complexes Me 2 (t-BuO) 2 FeLi 2 and Me 2 (t-BuO) 2 CoLi 2 , whereas Me 4 FeLi 2 methylates 1 at the keto group.

Starke erleichterung der carbonylolefinierung mit organoschwermetall-reagenzien durch eine diphenylphosphorylgruppe im reagenz☆

Abstract Carbonyl olefination with a lithiomethane, having besides the group P(O)Ph 2 at the methane C-atom an organo-heavy-metal group, occurs at low temperatures to give exclusively diphenylphosphoryl substituted olefins.