π-Facial Stereoselectivity

Rates and Stereoselectivities of Cycloadditions of Hexachlorocyclopentadiene to 7-Substituted Norbornadienes, and Photoelectron Spectral and Molecular Orbital Computational Investigations of Norbornadienes

Paul H. Mazzocchi, Barbara Stahly, John Harold Dodd, Nelson G. Rondan, L. N. Domelsmith, Melvin D. Rozeboom, Pierluigi Caramella, K. N. Houk

Research output: Contribution to journalArticle

88 Citations (Scopus)

Abstract

The partial rate factors for the Diels-Alder cycloadditions of hexachlorocyclopentadiene to 7-substituted norbornadienes in the four possible modes were measured. Syn-endo and anti-endo rates are essentially identical and decrease slightly as the effective electronegativity of the 7-substituent increases. The rates of the anti-exo cycloadditions decrease more rapidly in the same direction. Only the 7-tert-butoxy substituent gives significant acceleration of syn-endo attack. Both the ionization potentials (from photoelectron spectroscopy) of the π orbitals of norbornadienes and the rates and stereoselectivities of the cycloadditions are related to the effective electronegativities of the 7-substituents. Ab initio STO-3G calculations indicate that 7-substituents cause moderate shifts of the HOMO onto one of the norbornadiene double bonds but that reorientation of the directions in which the bonds point in space is also significantly influenced by these substituents. The ease of various distortions of the olefinic hydrogens out of plane, and perhaps alkene planarity itself, are influenced by the 7-substituents. A model for the influence of the 7-substituents on the orbitals of norbornadiene, and the stereochemistry of attack, is proposed which differs significantly from previous models but only partially accounts for -facial stereoselectivity in these systems.

Original languageEnglish (US)
Pages (from-to)6482-6490
Number of pages9
JournalJournal of the American Chemical Society
Volume102
Issue number21
DOIs
StatePublished - Jan 1 1980

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Stereoselectivity
Cycloaddition
Cycloaddition Reaction
Molecular orbitals
Photoelectrons
Electronegativity
Photoelectron Spectroscopy
Stereochemistry
Ionization potential
Alkenes
Photoelectron spectroscopy
Olefins
Hydrogen
hexachlorocyclopentadiene
Direction compound

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Mazzocchi, Paul H. ; Stahly, Barbara ; Dodd, John Harold ; Rondan, Nelson G. ; Domelsmith, L. N. ; Rozeboom, Melvin D. ; Caramella, Pierluigi ; Houk, K. N. / π-Facial Stereoselectivity : Rates and Stereoselectivities of Cycloadditions of Hexachlorocyclopentadiene to 7-Substituted Norbornadienes, and Photoelectron Spectral and Molecular Orbital Computational Investigations of Norbornadienes. In: Journal of the American Chemical Society. 1980 ; Vol. 102, No. 21. pp. 6482-6490.
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title = "π-Facial Stereoselectivity: Rates and Stereoselectivities of Cycloadditions of Hexachlorocyclopentadiene to 7-Substituted Norbornadienes, and Photoelectron Spectral and Molecular Orbital Computational Investigations of Norbornadienes",
abstract = "The partial rate factors for the Diels-Alder cycloadditions of hexachlorocyclopentadiene to 7-substituted norbornadienes in the four possible modes were measured. Syn-endo and anti-endo rates are essentially identical and decrease slightly as the effective electronegativity of the 7-substituent increases. The rates of the anti-exo cycloadditions decrease more rapidly in the same direction. Only the 7-tert-butoxy substituent gives significant acceleration of syn-endo attack. Both the ionization potentials (from photoelectron spectroscopy) of the π orbitals of norbornadienes and the rates and stereoselectivities of the cycloadditions are related to the effective electronegativities of the 7-substituents. Ab initio STO-3G calculations indicate that 7-substituents cause moderate shifts of the HOMO onto one of the norbornadiene double bonds but that reorientation of the directions in which the bonds point in space is also significantly influenced by these substituents. The ease of various distortions of the olefinic hydrogens out of plane, and perhaps alkene planarity itself, are influenced by the 7-substituents. A model for the influence of the 7-substituents on the orbitals of norbornadiene, and the stereochemistry of attack, is proposed which differs significantly from previous models but only partially accounts for -facial stereoselectivity in these systems.",
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π-Facial Stereoselectivity : Rates and Stereoselectivities of Cycloadditions of Hexachlorocyclopentadiene to 7-Substituted Norbornadienes, and Photoelectron Spectral and Molecular Orbital Computational Investigations of Norbornadienes. / Mazzocchi, Paul H.; Stahly, Barbara; Dodd, John Harold; Rondan, Nelson G.; Domelsmith, L. N.; Rozeboom, Melvin D.; Caramella, Pierluigi; Houk, K. N.

In: Journal of the American Chemical Society, Vol. 102, No. 21, 01.01.1980, p. 6482-6490.

Research output: Contribution to journalArticle

TY - JOUR

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T2 - Rates and Stereoselectivities of Cycloadditions of Hexachlorocyclopentadiene to 7-Substituted Norbornadienes, and Photoelectron Spectral and Molecular Orbital Computational Investigations of Norbornadienes

AU - Mazzocchi, Paul H.

AU - Stahly, Barbara

AU - Dodd, John Harold

AU - Rondan, Nelson G.

AU - Domelsmith, L. N.

AU - Rozeboom, Melvin D.

AU - Caramella, Pierluigi

AU - Houk, K. N.

PY - 1980/1/1

Y1 - 1980/1/1

N2 - The partial rate factors for the Diels-Alder cycloadditions of hexachlorocyclopentadiene to 7-substituted norbornadienes in the four possible modes were measured. Syn-endo and anti-endo rates are essentially identical and decrease slightly as the effective electronegativity of the 7-substituent increases. The rates of the anti-exo cycloadditions decrease more rapidly in the same direction. Only the 7-tert-butoxy substituent gives significant acceleration of syn-endo attack. Both the ionization potentials (from photoelectron spectroscopy) of the π orbitals of norbornadienes and the rates and stereoselectivities of the cycloadditions are related to the effective electronegativities of the 7-substituents. Ab initio STO-3G calculations indicate that 7-substituents cause moderate shifts of the HOMO onto one of the norbornadiene double bonds but that reorientation of the directions in which the bonds point in space is also significantly influenced by these substituents. The ease of various distortions of the olefinic hydrogens out of plane, and perhaps alkene planarity itself, are influenced by the 7-substituents. A model for the influence of the 7-substituents on the orbitals of norbornadiene, and the stereochemistry of attack, is proposed which differs significantly from previous models but only partially accounts for -facial stereoselectivity in these systems.

AB - The partial rate factors for the Diels-Alder cycloadditions of hexachlorocyclopentadiene to 7-substituted norbornadienes in the four possible modes were measured. Syn-endo and anti-endo rates are essentially identical and decrease slightly as the effective electronegativity of the 7-substituent increases. The rates of the anti-exo cycloadditions decrease more rapidly in the same direction. Only the 7-tert-butoxy substituent gives significant acceleration of syn-endo attack. Both the ionization potentials (from photoelectron spectroscopy) of the π orbitals of norbornadienes and the rates and stereoselectivities of the cycloadditions are related to the effective electronegativities of the 7-substituents. Ab initio STO-3G calculations indicate that 7-substituents cause moderate shifts of the HOMO onto one of the norbornadiene double bonds but that reorientation of the directions in which the bonds point in space is also significantly influenced by these substituents. The ease of various distortions of the olefinic hydrogens out of plane, and perhaps alkene planarity itself, are influenced by the 7-substituents. A model for the influence of the 7-substituents on the orbitals of norbornadiene, and the stereochemistry of attack, is proposed which differs significantly from previous models but only partially accounts for -facial stereoselectivity in these systems.

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