Enantioselective Preparation of 4-Substituted Cyclohexenes by Radical Fragmentation of Sulfoxides
作者:Christoph Imboden、Félix Villar、Philippe Renaud
DOI:10.1021/ol990859p
日期:1999.9.1
[GRAPHICS]Radical fragmentation of o-bromophenyl sulfoxides is reported. Starting from enantiomerically pure material, 4-substituted cyclohexene derivatives have been prepared with enantiomeric excesses between 70% and 86%, The key step of the process is a diastereoselective abstraction of a hydrogen atom by the initial aryl radical. The highest enantiomeric exesses have been obtained in the presence of aluminum Lewis acids.
Sodium Diisopropylamide-Mediated Dehydrohalogenations: Influence of Primary- and Secondary-Shell Solvation
作者:Yun Ma、Russell F. Algera、Ryan A. Woltornist、David B. Collum
DOI:10.1021/acs.joc.9b01428
日期:2019.9.6
1-chlorooctane is eliminated via disolvatedmonomer through a carbenoid mechanism. exo-2-Norbornyl chloride and bromide are also eliminated via disolvatedmonomer; a syn E2 mechanism is inferred for these substrates. The cis- and trans-4-tert-butylcyclohexyl bromides show a preference for the elimination of the cis isomer (kcis/ax/ktrans/eq = 10). Rate and isotopic labeling studies are consistent with