Asymmetric Addition Reactions with Optimized Selenium Electrophiles
摘要:
AbstractThe synthesis of various nonracemic diselenides by different methods is described. These diselenides are precursors for optically active selenium electrophiles. Their facial selectivity upon addition to styrene was investigated with respect to the chiral moiety neighboring the selenium. Diselenides 1 i, 1 n, and 1 v yielded addition products 7 with diastereomeric excesses up to 95%. Some diselenides, intermediates, and products of the addition reaction were investigated by 77Se NMR spectroscopy.
an understanding of how chiral amplification is possible, in particular based on non‐lineareffects. Interestingly, it has been proposed a quarter century ago that chiral catalysts, when not enantiopure might even be more enantioselective than their enantiopure counterparts. We show here that such hyperpositive non‐linear effect in asymmetric catalysis is indeed possible. An in‐depth study into the underlying
Functionalized Major-Groove and Minor-Groove Chiral Polybinaphthyls: Application in the Asymmetric Reaction of Aldehydes with Diethylzinc
作者:Qiao-Sheng Hu、Wei-Sheng Huang、Dilrukshi Vitharana、Xiao-Fan Zheng、Lin Pu
DOI:10.1021/ja972623r
日期:1997.12.1
have been synthesized by using the Suzuki coupling reaction and have been spectroscopically characterized. The application of these chiral polymers in the asymmetric addition of diethylzinc to aldehydes has been studied. A minor-groove polybinaphthyl is found to be an excellent catalyst for the asymmetricreaction of diethylzinc with a number of aldehydes. The molecular weight and the molecular weight
Asymmetric Addition Reactions with Optimized Selenium Electrophiles
作者:Thomas Wirth、Gianfranco Fragale
DOI:10.1002/chem.19970031123
日期:1997.11
AbstractThe synthesis of various nonracemic diselenides by different methods is described. These diselenides are precursors for optically active selenium electrophiles. Their facial selectivity upon addition to styrene was investigated with respect to the chiral moiety neighboring the selenium. Diselenides 1 i, 1 n, and 1 v yielded addition products 7 with diastereomeric excesses up to 95%. Some diselenides, intermediates, and products of the addition reaction were investigated by 77Se NMR spectroscopy.
Chiral Diselenides from Benzylamines: Catalysts in the Diethylzinc Addition to Aldehydes
作者:Thomas Wirth、Klaus J. Kulicke、Gianfranco Fragale
DOI:10.1002/hlca.19960790718
日期:1996.10.30
synthetic sequence (Scheme 1). Only 1 mol-% of these diselenides catalyzed very effectively the diethylzincaddition to various aromatic and α,β-unsaturated aldehydes yielding the secondary alcohols in up to 98% ee (Scheme 2 and Tables 1 and 2). An asymmetric amplification was observed with these catalysts. Detailed NMR studies were performed to characterize the catalytically active species.