Conformational Analysis of Triarylboranes

John F. Blount; Paolo Finocchiaro; Devens Gust; Kurt Mislow

doi:10.1021/ja00802a024

Conformational Analysis of Triarylboranes

John F. Blount, Paolo Finocchiaro, Devens Gust, Kurt Mislow

Molecular Sciences, School of (SMS)

Research output: Contribution to journal › Article › peer-review

145 Scopus citations

Abstract

An X-ray structure determination shows that trimesitylborane assumes a propeller conformation in the crystal lattice. The low-temperature ¹H-nmr spectra of diverse triarylboranes which have substituents other than hydrogen in all six ortho positions are consistent with this geometry in solution. At higher temperatures, the spectra reflect rapid stereoisomerizations, which are interpreted in terms of two-ring flip mechanisms. These processes have activation energies of ca. 14-16 kcal/mol, and separation of stereoisomers at ambient temperatures is therefore precluded.

Original language	English (US)
Pages (from-to)	7019-7029
Number of pages	11
Journal	Journal of the American Chemical Society
Volume	95
Issue number	21
DOIs	https://doi.org/10.1021/ja00802a024
State	Published - Oct 1 1973

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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N2 - An X-ray structure determination shows that trimesitylborane assumes a propeller conformation in the crystal lattice. The low-temperature 1H-nmr spectra of diverse triarylboranes which have substituents other than hydrogen in all six ortho positions are consistent with this geometry in solution. At higher temperatures, the spectra reflect rapid stereoisomerizations, which are interpreted in terms of two-ring flip mechanisms. These processes have activation energies of ca. 14-16 kcal/mol, and separation of stereoisomers at ambient temperatures is therefore precluded.

AB - An X-ray structure determination shows that trimesitylborane assumes a propeller conformation in the crystal lattice. The low-temperature 1H-nmr spectra of diverse triarylboranes which have substituents other than hydrogen in all six ortho positions are consistent with this geometry in solution. At higher temperatures, the spectra reflect rapid stereoisomerizations, which are interpreted in terms of two-ring flip mechanisms. These processes have activation energies of ca. 14-16 kcal/mol, and separation of stereoisomers at ambient temperatures is therefore precluded.

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Conformational Analysis of Triarylboranes

Abstract

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