Lithium Diisopropylamide-Mediated Ortholithiations: Lithium Chloride Catalysis.
- Resource Type
- Article
- Authors
- Gupta, Lekha; Hoepker, Alexander C.; Singh, Kanwal J.; Collum, David B.
- Source
- Journal of Organic Chemistry. 3/6/2009, Vol. 74 Issue 5, p2231-2233. 3p. 1 Chart.
- Subject
- *LITHIUM
*LITHIUM chloride
*CATALYSIS
*DISOPYRAMIDE
*ORGANOLITHIUM compounds
- Language
- ISSN
- 0022-3263
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-butyl- lithium 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. [ABSTRACT FROM AUTHOR]