Azaaldol Condensation of a Lithium Enolate Solvated by N,N,N′,N′-Tetramethylethylenediamine: Dimer-Based 1,2-Addition to Imines
The lithium enolate of tert-amylacetate solvated by N,N,N′,N′-tetramethylethylenediamine (TMEDA) is shown to be a doubly chelated dimer. Adding the dimeric enolate to 4-fluorobenzaldehyde-N-phenylimine affords an N-lithiated β-amino ester shown to be monomeric using 6Li and 15N NMR spectroscopies. R...
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Published in | Journal of the American Chemical Society Vol. 135; no. 10; pp. 4103 - 4109 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
WASHINGTON
American Chemical Society
13.03.2013
Amer Chemical Soc |
Subjects | |
Online Access | Get full text |
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Summary: | The lithium enolate of tert-amylacetate solvated by N,N,N′,N′-tetramethylethylenediamine (TMEDA) is shown to be a doubly chelated dimer. Adding the dimeric enolate to 4-fluorobenzaldehyde-N-phenylimine affords an N-lithiated β-amino ester shown to be monomeric using 6Li and 15N NMR spectroscopies. Rate studies using 19F NMR spectroscopy reveal reaction orders consistent with a transition structure of stoichiometry [(ROLi)2(TMEDA)2(imine)]⧧. Density functional theory computations explore several possible dimer-based transition structures with monodentate and bidentate coordination of TMEDA. Supporting rate studies using trans-N,N,N′,N′-1,2-tetramethylcyclohexanediamine showing analogous rates and rate law suggest that TMEDA is fully chelated. |
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Bibliography: | NIH RePORTER ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/ja400345c |