Studies on enantioselective allylic oxidation of olefins using peresters catalyzed by Cu(i)-complexes of chiral pybox ligands
作者:Sandeep K. Ginotra、Vinod K. Singh
DOI:10.1039/b612423b
日期:——
Enantioselective allylic oxidation of olefins with various peresters, using a catalytic amount of Cu(I)-pybox complex, can be tuned to achieve high asymmetric induction (up to 98% ee) by choosing a unique combination of a ligand and a perester at room temperature. The asymmetric induction in the reaction strongly depends on the nature of the substituents attached to the aryl ring of peresters. The
Catalytic enantioselective rearrangement of meso-epoxides mediated by chiral lithium amides in the presence of excess cross-linked polymer-bound lithium amides
作者:Atsushi Seki、Masatoshi Asami
DOI:10.1016/s0040-4020(02)00371-x
日期:2002.6
Insoluble polymer-bound achiral lithium dialkylamides were prepared from the corresponding cross-linked polymer-bound amines and butyllithium. The polymer-bound achiral reagent was applied to a catalytic enantioselective rearrangement of meso-epoxides as an in situ regenerating agent of a chiral lithiumamide. The efficiency of the catalytic system was improved, and chiral allylic alcohol derivatives
Enantioselective allylic oxidation catalyzed by chiral bisoxazoline-copper complexes
作者:Abha S. Gokhale、Alexander B.E. Minidis、Andreas Pfaltz
DOI:10.1016/0040-4039(95)00140-8
日期:1995.3
Copper(I) complexes prepared in situ from chiral bisoxazolines and Cu(I)OTf have been studied as catalysts for the allylic oxidation of cycloalkenes. Using 5 mol% of catalyst and tertbutyl perbenzoate as oxidant, optically active 2-cycloalkenyl benzoates were obtained in moderate to good yields. The highest enantiomeric excesses, 74% at 23 °C and up to 84% at lower temperatures, were observed for cyclopentene
Enantiopure Fluorous Bis(oxazolines): Synthesis and Applications in Catalytic Asymmetric Reactions
作者:Jerome Bayardon、Denis Sinou
DOI:10.1021/jo049853q
日期:2004.4.1
Various enantiopure fluorous bis(oxazolines) with fluorine content between 52.7 and 58.7% have been synthesized by a simple reaction sequence that involved the introduction of two fluorinated ponytails by alkylation of the corresponding nonfluorous bis(oxazolines). These new ligands have been used in palladium-catalyzed alkylation of rac-(E)-1,3-diphenylpropenyl acetate with carbon nucleophiles and
by lithiation of 2-imidazolines and subsequent reaction with dialkyl- or diarylhaloboranes. The corresponding 2-imidazolines were prepared by an efficient four-step sequence starting from N-tert-butoxycarbonyl-protected α-amino acids. C 2 -Symmetric methylenebis(imidazolines) were readily synthesized from chiral diamines by condensation with diethyl malonimidate. The bis(imidazolines) were used as