The role of organic fluorine in directing alkylation reactions via lithium chelation

K Tenza, J S Northen, D O'Hagan, A M Z Slawin

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

The fluorine of a fluoromethyl group displays a measurable chelation effect to lithium during a-methylation of an ester with lithium diisopropylamide (LDA) and methyl iodide. A series of esters is compared with F, H and 0, and the resultant diastereoselectivity is consistent with the intermediate capacity of F to chelate lithium relative to H and O. In a second system which involved comparing a tertiary organic fluorine with hydrogen, no such effect is apparent, most probably due to adverse steric effects. The absolute and relative stereochemistry of the predominant diastereoisomers are confirmed by X-ray crystallography of suitable crystalline derivatives in each case. It is concluded that there is a potential role for organic-bound fluorine to become involved in lithium chelation in well-designed enolate alkylation systems. (C) 2004 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)1779-1790
Number of pages12
JournalJournal of Fluorine Chemistry
Volume125
DOIs
Publication statusPublished - Nov 2004

Keywords

  • lithium enolates
  • organic fluorine
  • diastereoselectivity
  • ACID-DERIVATIVES
  • ADDITIONS

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