Nitroalkene (4+2) cycloadditions of achiral and chiral vinyl ethers. The stereochemical consequence of the Lewis acid promoter and studies toward the total synthesis of (+)-pretazettine
type: CreativeWork
description: Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\sb{2}$Cl$\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\sb2$Cl$\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.
abstract: Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\sb{2}$Cl$\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\sb2$Cl$\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.
author: Schnute, Mark Edward
language: eng
keywords: Chemistry, Organic
date published: 2011-05-07T13:38:43Z
date modified: 2026-07-22T22:25:19Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/22403