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.
First Detection of a Selenenyl Fluoride ArSe?F by NMR Spectroscopy: The Nature of Ar2Se2/XeF2 and ArSe?SiMe3/XeF2 Reagents
作者:Helmut Poleschner、Konrad Seppelt
DOI:10.1002/chem.200400596
日期:2004.12.17
Arylselenenyl fluorides ArSeF are obtained from diselenides Ar2Se2 or arylselenotrimethylsilanes ArSe-SiMe3, and XeF2. They are detected by low-temperature 19F and 77Se NMRspectroscopy. Substitution in the ortho position of the aromatic ring to provide electronic or steric protection is a requirement for their formation. ArSe--F compounds decompose according to 3 ArSe-F-->[ArSe-SeF2Ar]+ArSe-F-->ArSeF3+Ar2Se2
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.