analysis. These new bis(oxazolines) are efficient chiralligands in the asymmetriccatalysis of the Diels-Alder reaction ofN-alkenoyl-oxazolidin-2-one derivatives since endo cycloadducts are obtained with up to 94% ee. Different Lewis acids were tested, the best one being the Mg(II) cation derived from the corresponding triflate. A remarkable feature of such new chiralligands is the low solubility in
Remarkable solvent effect on the enantioface selectivity in the Diels-Alder reaction catalyzed by an Aluminum complex of a newly prepared chiral menthol derivative
作者:Go Naraku、Kiyoto Hori、Yoshio N. Ito、Tsutomu Katsuki
DOI:10.1016/s0040-4039(97)10202-7
日期:1997.11
Reversal of enantioface selectivity was observed by merely switching die solvent from CH2Cl2 (enantiomer ratio of the adduct = 91:9) to THF (14:86) in the asymmetric Diels-Alder reaction catalyzed by the aluminum complex of a newly prepared chiral menthol derivative. Negative nonlinear effect on the relationship between enantiomeric excesses of the reaction product and optical purities of the ligand was observed for the reaction in CH2Cl2 whilst linear relationship for that in THF. (C) 1997 Elsevier Science Ltd.
Highly Efficient Asymmetric Lewis Acid Catalysis with Platinum Group Complexes of Conformationally Flexible 1,3-Butadiene-Bridged Diphosphines, NUPHOS
作者:Simon Doherty、Colin R. Newman、Rakesh K. Rath、He-Kuan Luo、Mark Nieuwenhuyzen、Julian G. Knight
DOI:10.1021/ol035409i
日期:2003.10.1
[GRAPHICS]Palladium and platinum complexes of conformationally flexible 1,3-butadiene-bridged diphosphines NUPHOS can be resolved with (S)-BINOL at elevated temperatures to afford diastereopure delta-[(NUPHOS)M(S)-BINOL}] (M = Pd, Pt). The homochiral Lewis acid complexes delta-[(NUPHOS)M]-[OTf](2), generated by protonation of delta-[(NUPHOS)M(S)-BINOL}] with trifluoromethanesulfonic acid, catalyze the Dlels-Alder reaction between acryloyl-N-oxazolidinones and cyclopentadiene to give ee values up to 96%. The corresponding enantiopure dichlorides delta-[(NUPHOS)PtCl2] react with AgClO4 to form highly efficient catalysts that give good endo/exo selectivities and high endo enantioselectivity.
Bis(oxazoline)copper(II) complexes as chiral catalysts for the enantioselective Diels-Alder reaction
作者:David A. Evans、Scott J. Miller、Thomas Lectka
DOI:10.1021/ja00067a091
日期:1993.7
observations on the utility of chiral Cu(1I) bis(oxazoline) complexes as Lewis acids in the catalysis of these reactions. Attractive attributes of this catalyst system include an expanded scope of utilizable dienophiles and a clearly interpretable geometry for the catalyst-dienophile complex which rationalizes the sense of asymmetric induction for the cycloaddition process.