Studies on the molecular geometry of the norbornyl cation. I. The synthesis and acetolysis of the exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates

E. J. Corey, Richard S Glass

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Abstract

4,5-exo-Trimethylene-2-norbornene (10) has been synthesized from a monosubstituted cyclopentadiene 9 using an intramolecular Diels-Alder reaction, and from this intermediate exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates (11, R = Ts, and 16, R = Ts) have been prepared. These sulfonates undergo acetolysis (25°) at relative rates of 8.6:1. The ratio of rate constants (25°) for acetolysis of the exo-sulfonate 11, R = Ts, and 2-exo-norbornyl p-toluenesulfonate is 1:85, whereas the corresponding ratio for the endo-sulfonate 16, R = Ts, and 2-endo-norbornyl p-toluenesulfonate is 1:2.5. The depressed rate for the tricyclic exo-sulfonate 11, R = Ts, relative to 2-exo-norbornyl p-toluenesulfonate is readily explained in terms of bridging of carbon in the transition state for ionization, but seems to be contrary to expectations based on ionization to a localized (classical) carbonium ion. Thus, the present results favor the bridged-ion mechanism for acetolysis of 2-exo-norbornyl arene-sulfonates.

Original languageEnglish (US)
Pages (from-to)2600-2610
Number of pages11
JournalJournal of the American Chemical Society
Volume89
Issue number11
StatePublished - 1967
Externally publishedYes

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Ionization
Cations
Positive ions
Geometry
Ions
Rate constants
Cyclopentanes
Carbon
Cycloaddition Reaction
4-toluenesulfonic acid
cyclopropane

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Studies on the molecular geometry of the norbornyl cation. I. The synthesis and acetolysis of the exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates",
abstract = "4,5-exo-Trimethylene-2-norbornene (10) has been synthesized from a monosubstituted cyclopentadiene 9 using an intramolecular Diels-Alder reaction, and from this intermediate exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates (11, R = Ts, and 16, R = Ts) have been prepared. These sulfonates undergo acetolysis (25°) at relative rates of 8.6:1. The ratio of rate constants (25°) for acetolysis of the exo-sulfonate 11, R = Ts, and 2-exo-norbornyl p-toluenesulfonate is 1:85, whereas the corresponding ratio for the endo-sulfonate 16, R = Ts, and 2-endo-norbornyl p-toluenesulfonate is 1:2.5. The depressed rate for the tricyclic exo-sulfonate 11, R = Ts, relative to 2-exo-norbornyl p-toluenesulfonate is readily explained in terms of bridging of carbon in the transition state for ionization, but seems to be contrary to expectations based on ionization to a localized (classical) carbonium ion. Thus, the present results favor the bridged-ion mechanism for acetolysis of 2-exo-norbornyl arene-sulfonates.",
author = "Corey, {E. J.} and Glass, {Richard S}",
year = "1967",
language = "English (US)",
volume = "89",
pages = "2600--2610",
journal = "Journal of the American Chemical Society",
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T1 - Studies on the molecular geometry of the norbornyl cation. I. The synthesis and acetolysis of the exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates

AU - Corey, E. J.

AU - Glass, Richard S

PY - 1967

Y1 - 1967

N2 - 4,5-exo-Trimethylene-2-norbornene (10) has been synthesized from a monosubstituted cyclopentadiene 9 using an intramolecular Diels-Alder reaction, and from this intermediate exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates (11, R = Ts, and 16, R = Ts) have been prepared. These sulfonates undergo acetolysis (25°) at relative rates of 8.6:1. The ratio of rate constants (25°) for acetolysis of the exo-sulfonate 11, R = Ts, and 2-exo-norbornyl p-toluenesulfonate is 1:85, whereas the corresponding ratio for the endo-sulfonate 16, R = Ts, and 2-endo-norbornyl p-toluenesulfonate is 1:2.5. The depressed rate for the tricyclic exo-sulfonate 11, R = Ts, relative to 2-exo-norbornyl p-toluenesulfonate is readily explained in terms of bridging of carbon in the transition state for ionization, but seems to be contrary to expectations based on ionization to a localized (classical) carbonium ion. Thus, the present results favor the bridged-ion mechanism for acetolysis of 2-exo-norbornyl arene-sulfonates.

AB - 4,5-exo-Trimethylene-2-norbornene (10) has been synthesized from a monosubstituted cyclopentadiene 9 using an intramolecular Diels-Alder reaction, and from this intermediate exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates (11, R = Ts, and 16, R = Ts) have been prepared. These sulfonates undergo acetolysis (25°) at relative rates of 8.6:1. The ratio of rate constants (25°) for acetolysis of the exo-sulfonate 11, R = Ts, and 2-exo-norbornyl p-toluenesulfonate is 1:85, whereas the corresponding ratio for the endo-sulfonate 16, R = Ts, and 2-endo-norbornyl p-toluenesulfonate is 1:2.5. The depressed rate for the tricyclic exo-sulfonate 11, R = Ts, relative to 2-exo-norbornyl p-toluenesulfonate is readily explained in terms of bridging of carbon in the transition state for ionization, but seems to be contrary to expectations based on ionization to a localized (classical) carbonium ion. Thus, the present results favor the bridged-ion mechanism for acetolysis of 2-exo-norbornyl arene-sulfonates.

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