Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr4/PPh3 and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

Abstract
Cholesterol reacts under Appel conditions (CBr4/PPh3) to give 3,5-cholestadiene (elimination) and 3β-bromocholest-5-ene (substitution with retention of configuration). Thus, the bromination of cholesterol deviates from the stereochemistry of the standard Appel mechanism due to participation of the Δ5 π-electrons. In contrast, the subsequent azidolysis (NaN3/DMF) of 3β-bromocholest-5-ene proceeds predominantly by Walden inversion (SN2) affording 3α-azidocholest-5-ene. The structures of all relevant products were revealed by X-ray single crystal structure analyses, and the NMR data are in agreement to the reported ones. In light of these findings, we herein correct the previous stereochemical assignments reported by one of us in the Beilstein J. Org. Chem. 2015, 11, 1922–1932 and the Monatsh. Chem. 2018, 149, 505–517.
Main Authors
Format
Articles Research article
Published
2023
Series
Subjects
Publication in research information system
Publisher
Beilstein Institut
The permanent address of the publication
https://urn.fi/URN:NBN:fi:jyu-202302061643Use this for linking
Review status
Peer reviewed
ISSN
2195-951X
DOI
https://doi.org/10.3762/bjoc.19.9
Language
English
Published in
Beilstein Journal of Organic Chemistry
Citation
  • Schumacher, C., Ward, J. S., Rissanen, K., Bolm, C., & Ramadan El Sayed Aly, M. (2023). Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr4/PPh3 and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior. Beilstein Journal of Organic Chemistry, 19, 91-99. https://doi.org/10.3762/bjoc.19.9
License
CC BY 4.0Open Access
Additional information about funding
We are grateful to the Alexander von Humboldt Foundation and the Verband der Chemischen Industrie e.V. for support of K. R. (AvH research award) and C. S. (Kekulé scholarship), respectively. The support of Port Said University is kindly acknowledged.
Copyright© Authors 2023

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