1,5-Asymmetric Induction in Squarate Cascades. Conformational Control of Helicity by Chiral Amino Substituants during Conrotatory Octatetraene Cyclization Prior to β-Elimination

Leo A. Paquette, Jinsung Tae

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Both the sigmatropic and electrocyclic rearrangement pathways that can arise when a pair of alkenyl anions are added to a squarate ester have high stereochemical demands. The distinction is nontrivial. When cis addition occurs initially, the stereoinduction that materializes at this point is fully transmitted into the product (s). The more commonly observed trans addition exhibits fleeting stereochemical consequences because of rapid equilibration of the octatetraenyl intermediates. In this instance, product distribution is governed by the relative rates of conrotatory cyclization at this advanced stage. Herein reported is a complete dissection of a squarate cascade when a stereogenic center attached to an amino substituent effects 1,5-asymmetric induction prior to β-elimination of the entire fragment. Deuterium labeling permits a direct measure of the contrasting kinetic imbalances associated with the two possible modes of alkenyl anion addition. Furthermore, quantitative analysis of the partitioning experienced by the two helical octatetraenes is readily accomplished. This work constitutes the first example where a complete dynamic profile for these complex processes has been possible. The fact that long-range asymmetric induction has been instrumental in solving the mechanistic puzzle is noteworthy.

Original languageEnglish
Pages (from-to)2022-2030
Number of pages9
JournalJournal of Organic Chemistry
Volume63
Issue number6
Publication statusPublished - 1998 Mar 20

Fingerprint

Cyclization
Anions
Dissection
Deuterium
Labeling
Esters
Kinetics
Chemical analysis

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

@article{7af08d75ca87496a9ace412d0e1b24f6,
title = "1,5-Asymmetric Induction in Squarate Cascades. Conformational Control of Helicity by Chiral Amino Substituants during Conrotatory Octatetraene Cyclization Prior to β-Elimination",
abstract = "Both the sigmatropic and electrocyclic rearrangement pathways that can arise when a pair of alkenyl anions are added to a squarate ester have high stereochemical demands. The distinction is nontrivial. When cis addition occurs initially, the stereoinduction that materializes at this point is fully transmitted into the product (s). The more commonly observed trans addition exhibits fleeting stereochemical consequences because of rapid equilibration of the octatetraenyl intermediates. In this instance, product distribution is governed by the relative rates of conrotatory cyclization at this advanced stage. Herein reported is a complete dissection of a squarate cascade when a stereogenic center attached to an amino substituent effects 1,5-asymmetric induction prior to β-elimination of the entire fragment. Deuterium labeling permits a direct measure of the contrasting kinetic imbalances associated with the two possible modes of alkenyl anion addition. Furthermore, quantitative analysis of the partitioning experienced by the two helical octatetraenes is readily accomplished. This work constitutes the first example where a complete dynamic profile for these complex processes has been possible. The fact that long-range asymmetric induction has been instrumental in solving the mechanistic puzzle is noteworthy.",
author = "Paquette, {Leo A.} and Jinsung Tae",
year = "1998",
month = "3",
day = "20",
language = "English",
volume = "63",
pages = "2022--2030",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "6",

}

TY - JOUR

T1 - 1,5-Asymmetric Induction in Squarate Cascades. Conformational Control of Helicity by Chiral Amino Substituants during Conrotatory Octatetraene Cyclization Prior to β-Elimination

AU - Paquette, Leo A.

AU - Tae, Jinsung

PY - 1998/3/20

Y1 - 1998/3/20

N2 - Both the sigmatropic and electrocyclic rearrangement pathways that can arise when a pair of alkenyl anions are added to a squarate ester have high stereochemical demands. The distinction is nontrivial. When cis addition occurs initially, the stereoinduction that materializes at this point is fully transmitted into the product (s). The more commonly observed trans addition exhibits fleeting stereochemical consequences because of rapid equilibration of the octatetraenyl intermediates. In this instance, product distribution is governed by the relative rates of conrotatory cyclization at this advanced stage. Herein reported is a complete dissection of a squarate cascade when a stereogenic center attached to an amino substituent effects 1,5-asymmetric induction prior to β-elimination of the entire fragment. Deuterium labeling permits a direct measure of the contrasting kinetic imbalances associated with the two possible modes of alkenyl anion addition. Furthermore, quantitative analysis of the partitioning experienced by the two helical octatetraenes is readily accomplished. This work constitutes the first example where a complete dynamic profile for these complex processes has been possible. The fact that long-range asymmetric induction has been instrumental in solving the mechanistic puzzle is noteworthy.

AB - Both the sigmatropic and electrocyclic rearrangement pathways that can arise when a pair of alkenyl anions are added to a squarate ester have high stereochemical demands. The distinction is nontrivial. When cis addition occurs initially, the stereoinduction that materializes at this point is fully transmitted into the product (s). The more commonly observed trans addition exhibits fleeting stereochemical consequences because of rapid equilibration of the octatetraenyl intermediates. In this instance, product distribution is governed by the relative rates of conrotatory cyclization at this advanced stage. Herein reported is a complete dissection of a squarate cascade when a stereogenic center attached to an amino substituent effects 1,5-asymmetric induction prior to β-elimination of the entire fragment. Deuterium labeling permits a direct measure of the contrasting kinetic imbalances associated with the two possible modes of alkenyl anion addition. Furthermore, quantitative analysis of the partitioning experienced by the two helical octatetraenes is readily accomplished. This work constitutes the first example where a complete dynamic profile for these complex processes has been possible. The fact that long-range asymmetric induction has been instrumental in solving the mechanistic puzzle is noteworthy.

UR - http://www.scopus.com/inward/record.url?scp=0001371532&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001371532&partnerID=8YFLogxK

M3 - Article

VL - 63

SP - 2022

EP - 2030

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 6

ER -