Ketone enolization with lithium dialkylamides: the effects of structure,solvation, and mixed aggregates with excess butyllithium |
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| Authors: | Pratt Lawrence M Newman Anthony Cyr Jason St Johnson Harry Miles Benjamin Lattier April Austin Elizabeth Henderson Susan Hershey Brad Lin Ming Balamraju Yuvaraju Sammonds Laurel Cheramie Jeffery Karnes Jonathan Hymel Ellen Woodford Brittini Carter Carl |
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| Institution: | Department of Chemistry, Fisk University, Nashville, Tennessee 37208, USA. lpratt@fisk.edu |
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| 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. |
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