Lithium Diisopropylamide-Mediated Ortholithiations: Lithium Chloride Catalysis

Ortholithiations of a range of arenes mediated by lithium diisopropylamide (LDA) in THF at −78 °C reveal substantial accelerations by as little as 0.5 mol % of LiCl (relative to LDA). Substrate dependencies suggest a specific range of reactivity within which the LiCl catalysis is optimal. Standard p...

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Bibliographic Details
Published in:Journal of organic chemistry 2009-03, Vol.74 (5), p.2231-2233
Main Authors: Gupta, Lekha, Hoepker, Alexander C, Singh, Kanwal J, Collum, David B
Format: Article
Language:English
Subjects:
Catalysis
Chemical reactivity
Chemistry
Exact sciences and technology
Kinetics and mechanisms
Lithium Chloride - chemistry
Molecular Structure
Organic chemistry
Organometallic Compounds - chemical synthesis
Organometallic Compounds - chemistry
Propylamines - chemistry
Reactivity and mechanisms
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Summary:Ortholithiations of a range of arenes mediated by lithium diisopropylamide (LDA) in THF at −78 °C reveal substantial accelerations by as little as 0.5 mol % of LiCl (relative to LDA). Substrate dependencies suggest a specific range of reactivity within which the LiCl catalysis is optimal. Standard protocols with unpurified commercial samples of n-butyllithium to prepare LDA or commercially available LDA show marked batch-dependent ratesup to 100-foldthat could prove significant to the unwary practitioner. Other lithium salts elicit more modest accelerations. The mechanism is not discussed.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo802713y