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Lithium diisopropylamide-mediated ortholithiations: lithium chloride catalysis.

ABSTRACT: Ortholithiations of a range of arenes mediated by lithium diisopropylamide (LDA) in THF at -78 degrees 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.

SUBMITTER: Gupta L

PROVIDER: S-EPMC2765536 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Lithium diisopropylamide-mediated ortholithiations: lithium chloride catalysis.

Gupta Lekha L Hoepker Alexander C AC Singh Kanwal J KJ Collum David B DB

The Journal of organic chemistry 20090301 5

Ortholithiations of a range of arenes mediated by lithium diisopropylamide (LDA) in THF at -78 degrees 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 ...[more]

PMID: 19191711

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