title: 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.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Lekha
authors.initials: L
authors.lastname: Gupta
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Hoepker
authors.forename: Kanwal J
authors.initials: KJ
authors.lastname: Singh
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D002384:Catalysis; D018021:Lithium Chloride / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011437:Propylamines / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D011437:Propylamines; C007442:diisopropylamine; D018021:Lithium Chloride