Studies on the stereochemical assignment of 3-acylidene 2-oxindoles.
The designation of E/Z-geometrical isomers in 3-acylidene 2-oxindoles by NMR spectroscopy can lead to erroneous assignment of alkene stereochemistry because of the narrow chemical shift range observed over a large series of analogues. In contrast, UV-Vis spectroscopy offers a convenient and more reliable method for alkene stereochemical assignment. A combination of X-ray crystallography and theoretical studies shows that the observed differences in UV-Vis spectroscopic behaviour relate to the twisted conformation of the Z-isomers that provides reduced conjugation and weaker hypsochromic (blue-shifted) absorbances relative to those of the E-isomers.
Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK. j.harrity@sheffield.ac.uk.
Steven J
SJ
Edeson
Julong
J
Jiang
Stephen
S
Swanson
Panayiotis A
PA
Procopiou
Harry
H
Adams
Anthony J H M
AJ
Meijer
Joseph P A
JP
Harrity
D000447:Aldehydes / Q000737:chemistry; D018360:Crystallography, X-Ray; D004583:Electrons; D007211:Indoles / Q000737:chemistry*; D008958:Models, Molecular; D000078183:Oxindoles; D066244:Proton Magnetic Resonance Spectroscopy; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013816:Thermodynamics
D000447:Aldehydes; D007211:Indoles; D000078183:Oxindoles; C022960:2-oxindole; C116609:3-hydroxybutanal