X=y-zh systems as potential 1,3-dipoles-5. Intramolecular cycloadditions of imines of α-amino acid esters
Azomethine ylides are readily generated from imines of α-amino acid esters by a formal 1,2-H shift. A suitably positioned unactivated double or triple bond in either of the two precursors of the imines (aldehyde or α-amino ester) leads to an intramolecular cycloaddition generating fused ring systems in good yield. Cis stereochemistry is assigned to the newly created ring junction of the cycloadducts based on NOE difference spectroscopy and, in the case of 8a, by a single crystal X-ray structure. Equilibration of the kinetically formed dipole leads to mixtures of epimeric cycloadducts for imines of phenylglycine methyl ester but equilibration is not observed for other imines. Reasons for this are discussed. The intramolecular cycloaddition is sensitive to ring size with 6/5 and 5/5 cis-fused systems being most easily formed depending in which moiety (aldehyde or amino acid) the dipolarophile is located. Intramolecular trapping of the azomethine ylide by an alkyne is accompanied by variable amounts of aromatized pyrrolic products. © 1985.
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- Organic Chemistry
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- 3101 Biochemistry and cell biology
- 0305 Organic Chemistry
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Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Related Subject Headings
- Organic Chemistry
- 3405 Organic chemistry
- 3404 Medicinal and biomolecular chemistry
- 3101 Biochemistry and cell biology
- 0305 Organic Chemistry
- 0304 Medicinal and Biomolecular Chemistry