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Updated: Jul 18, 2026
08:12
A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Practical approach to alpha- or gamma-heterosubstituted enoic acids
Julia L Shamshina1, Timothy S Snowden
1Department of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL 34587-0336, USA.
Organic Letters
|December 1, 2006
Summary
Mercaptans undergo alpha-substitution on dichloroepoxides, while hydroxide promotes gamma-substitution with allylic transposition. Alkoxide reactions show regioselectivity based on alkene substitution patterns.
Area of Science:
- Organic Chemistry
- Reaction Mechanisms
Background:
- Alkenyl trichloromethyl carbinols are versatile synthetic precursors.
- Understanding nucleophilic substitution reactions is crucial in organic synthesis.
Purpose of the Study:
- To investigate the reaction pathways of alkenyl trichloromethyl carbinols with different nucleophiles.
- To elucidate the mechanisms of substitution (S(N)2 and S(N)2') and regioselectivity.
Main Methods:
- Treatment of alkenyl trichloromethyl carbinols with various nucleophiles (mercaptans, hydroxide, alkoxides) under protic basic conditions.
- Analysis of reaction products to determine substitution patterns and stereochemistry.
Main Results:
- Mercaptans react via S(N)2 alpha-substitution of intermediate alkenyl gem-dichloroepoxides.
- Hydroxide leads to S(N)2' gamma-substitution with stereoselective allylic transposition.
- Alkoxide regioselectivity is influenced by the degree of alkene substitution.
Conclusions:
- The nucleophile dictates the reaction pathway (alpha- vs. gamma-substitution).
- Stereoselective allylic transposition occurs with hydroxide.
- Alkene substitution pattern controls regioselectivity in alkoxide reactions.
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