STEREOCHEMISTRY OF DIPHENYLBENZENES. PREPARATION OF STEREOISOMERIC 3,6-DI-(2,4-DIMETHYLPHENYL)-2,5-DIBROMOHYDROQUINONES AND THEIR DERIVATIVES. IX<sup>1</sup>

Browning, Ethel; Adams, Roger

doi:10.1021/ja01373a051

Cited by 13 publications

(3 citation statements)

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“…We are aware of only one other example of diastereotopic atoms in molecules (the highly sterically hindered 1-(4-X-phenyl)-8-(2-methylphenyl)naphthalenes) that do not possess either a stereogenic or a prostereogenic 11 center. The diastereomers of 3,6-di(2,4-dimethylphenyl)-2,5-dibromohydroquinone, which can be interconverted at >200 °C, represent a similar relationship …”

Section: Discussionmentioning

confidence: 98%

Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

Staley

Kehlbeck

2001

J. Am. Chem. Soc.

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A novel low-temperature intramolecular exchange was detected by (13)C NMR spectrometry in the Na(+) and K(+) salts of the title compound. The process causes the pairwise exchange in the dianion ring of C(2"), C(3"), and C(4") with C(8"), C(7"), and C(6"), respectively. The free energy of activation (DeltaG()(exch)) for the dipotassium salt (2(2-)/2K(+)) in THF-d(8) at 230 K is 12.6 kcal mol(-1). Two key questions are addressed: (1) Why are these carbons anisochronous and (2) what is the mechanism of exchange? NMR data for 1-cyclooctatetraenylnaphthalenedipotassium (3(2-)/2K(+)) as well as ab initio HF/3-21G(++) calculations for 3, 3(2-), and 3(2-)/2K(+) indicate that the nonequivalence is due to both slow rotation across a barrier at which the naphthalene and COT(2)(-) rings are approximately coplanar and slow inversion of the neutral COT ring. This results in the noteworthy circumstance of diastereotopic carbons being observed in a molecule that does not possess either a stereogenic or a prostereogenic center. Comparison of DeltaG()(exch) and DeltaG(++)(BS) for 2(2-)/2K(+) with the corresponding values for 2(2-)/2Na(+) and 2(2-)/2Li(+) and of DeltaG(++)(exch) with DeltaG(++) for ring inversion in 1,4-dicyclooctatetraenylnaphthalene leads to the conclusion that COT(2-) ring rotation and COT ring inversion both contribute to exchange in 2(2-)/2K(+) in a 3:1 ratio, but that exchange occurs exclusively by ring rotation in 2(2-)/2Li(+). The latter result is attributed to looser ion pairing in the dilithium (and disodium) salts.

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Section: Discussionmentioning

confidence: 98%

Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

Staley

Kehlbeck

2001

J. Am. Chem. Soc.

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“…The reaction of benzoquinone with m-xylene and mesitylene affords the corresponding tetramethyl- (36) and hexamethyldihydroxy-p-terphenyls (127); in each case the yield was 44 per cent. Similarly, 2' ,5'-dihydroxy-4-methyl-pterphenyl is obtained from 2-p-tolylbenzoquinone (21).…”

Section: Additions To Dienesmentioning

confidence: 98%

The Synthesis of Substituted Terphenyls

Ames¹

1958

Chem. Rev.

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“…Experimentally, only p-diphenylbenzene derivatives have as yet been investigated. The possibility for the existence of a meso and a racemic modification of substituted p-diphenylbenzenes of Type 2 teas demonstrated by the isolation (25) of two stereoisomeric compounds, CXIX and CXX, prepared by bronination of CXVIII, a product from the reaction of m-xylene, quinone, and aluminum chloride. Each of the two isomers formed individual series of derivatives but oxidized to the same quinone CXXI.…”

Section: Polyphenyl Systemsmentioning

confidence: 99%

The Stereochemistry of Diphenyls and Analogous Compounds.

Adams¹,

Yuan²

1933

Chem. Rev.

153

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STEREOCHEMISTRY OF DIPHENYLBENZENES. PREPARATION OF STEREOISOMERIC 3,6-DI-(2,4-DIMETHYLPHENYL)-2,5-DIBROMOHYDROQUINONES AND THEIR DERIVATIVES. IX¹

Abstract: Fraction 2 was analyzed with the following results.

Cited by 13 publications

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Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

The Synthesis of Substituted Terphenyls

The Stereochemistry of Diphenyls and Analogous Compounds.

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STEREOCHEMISTRY OF DIPHENYLBENZENES. PREPARATION OF STEREOISOMERIC 3,6-DI-(2,4-DIMETHYLPHENYL)-2,5-DIBROMOHYDROQUINONES AND THEIR DERIVATIVES. IX1

Abstract: Fraction 2 was analyzed with the following results.

Cited by 13 publications

References 0 publications

Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

Mechanism of a Novel Exchange Process in Alkali Metal Salts of 1,5-Dicyclooctatetraenylnaphthalene Dianion

The Synthesis of Substituted Terphenyls

The Stereochemistry of Diphenyls and Analogous Compounds.

Contact Info

Product

Resources

About

STEREOCHEMISTRY OF DIPHENYLBENZENES. PREPARATION OF STEREOISOMERIC 3,6-DI-(2,4-DIMETHYLPHENYL)-2,5-DIBROMOHYDROQUINONES AND THEIR DERIVATIVES. IX¹