Regio- and Diastereoselective Copper(I)-Catalyzed Allylic Substitution of δ-Hydroxy Allylic Chlorides by a Silicon Nucleophile
作者:Chinmoy K. Hazra、Elisabeth Irran、Martin Oestreich
DOI:10.1002/ejoc.201300493
日期:2013.8
A perfectly γ-selectivecopper(I)-catalyzedallylic substitution of protected δ-hydroxy allylic chlorides with a silicon nucleophile generated by Si–B bond activation provides diastereoselective access to β-hydroxy α-chiralallylicsilanes with an anti relative configuration. The high levels of diastereocontrol of this rare allylic displacement are interpreted according to a model suggested by Nakamura
Stereoselective synthesis of substituted dienes by the double ortho ester Claisen rearrangement
作者:Suk-pyo Hong、Sung-jun Yoon、Byung-chan Yu
DOI:10.1016/j.tetlet.2004.12.015
日期:2005.1
This letter shows the highly stereoselective synthesis of substituted (E)-1,3-dienes from substituted propargylic diols via the double ortho ester Claisenrearrangement. The cyclohexyl-substituted diene undergoes thermal Diels–Alder cycloaddition with maleic anhydride to produce the corresponding bicyclic diester in highly stereoselective manner.
4-Ethenylidene-2-oxazolidinones 2, 6, and 9 are prepared in reasonable yields by the reaction of 2-butyn-1,4-diol biscarbamates in the presence of catalytic amounts of Pd-2(dba)(3) . CHCl3 (0.005 equiv) ad triethylamine (0.1 equiv). The allenic three carbons are not aligned straight, but considerably distorted (173.6 degrees); the enamine double bond is reactive toward unsaturated amides (providng 4) and methyl vinyl ketone (providing 10). (C) 1997 Elsevier Science Ltd.
An Efficient, Stereoselective Approach to <i>s</i><i>yn</i>-1,2-Diols Protected as Cyclic Carbonates
Enantioenriched 4-hydroxyalk-2-ynyl carbonates (or benzoates) have been prepared by stereoselective zinc-mediated addition of alkyl 2-propynyl carbonates (or their benzoate analogues) to aldehydes. Their partial reduction to Z-olefins followed by cyclization under mild Pd-catalyzed conditions allowed a straightforward access to enantioenriched syn-1,2-diols protected as cyclic carbonates.