title: Ketone enolization with lithium dialkylamides: the effects of structure, solvation, and mixed aggregates with excess butyllithium.
abstract: The effects of lithium dialkylamide structure, mixed aggregate formation, and solvation on the stereoselectivity of ketone enolization were examined. Of the lithium dialkylamides examined, lithium tetramethylpiperidide (LiTMP) in THF resulted in the best enolization selectivity. The stereoselectivity was further improved in the presence of a LiTMP-butyllithium mixed aggregate. The use of less polar solvents reduced the enolization stereoselectivity. Ab initio calculations predict LDA and LiTMP to form mixed cyclic dimers in ethereal solvents. The calculations also predict LiTMP-alkyllithium mixed aggregates to competitively inhibit the formation of less stereoselective LiTMP-lithium enolate mixed aggregates.
authors.affiliation: Department of Chemistry, Fisk University, Nashville, Tennessee 37208, USA. lpratt@fisk.edu
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Pratt
authors.forename: Anthony
authors.initials: A
authors.lastname: Newman
authors.forename: Jason St
authors.initials: JS
authors.lastname: Cyr
authors.forename: Harry
authors.initials: H
authors.lastname: Johnson
authors.forename: Benjamin
authors.initials: B
authors.lastname: Miles
authors.forename: April
authors.initials: A
authors.lastname: Lattier
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Austin
authors.forename: Susan
authors.initials: S
authors.lastname: Henderson
authors.forename: Brad
authors.initials: B
authors.lastname: Hershey
authors.forename: Ming
authors.initials: M
authors.lastname: Lin
authors.forename: Yuvaraju
authors.initials: Y
authors.lastname: Balamraju
authors.forename: Laurel
authors.initials: L
authors.lastname: Sammonds
authors.forename: Jeffery
authors.initials: J
authors.lastname: Cheramie
authors.forename: Jonathan
authors.initials: J
authors.lastname: Karnes
authors.forename: Ellen
authors.initials: E
authors.lastname: Hymel
authors.forename: Brittini
authors.initials: B
authors.lastname: Woodford
authors.forename: Carl
authors.initials: C
authors.lastname: Carter
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D008401:Gas Chromatography-Mass Spectrometry; D007659:Ketones / Q000737:chemistry*; D018020:Lithium Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry; D011437:Propylamines / Q000737:chemistry; D012997:Solvents; D013237:Stereoisomerism
chemical_list: D007659:Ketones; D018020:Lithium Compounds; D009942:Organometallic Compounds; D011437:Propylamines; D012997:Solvents; C046771:butyllithium; C007442:diisopropylamine