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n-π-Interaction in Enamines and Enaminoketones. A 15N-NMR. Study

✍ Scribed by Willi Schwotzer; Wolfgang Von Philipsborn

Publisher
John Wiley and Sons
Year
1977
Tongue
German
Weight
415 KB
Volume
60
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

^15^N‐Chemical shifts of 32 enamines, 11 enaminoketones and 28 closely related amines have been determined with the isotope in natural abundance. In order to eliminate substituent effects, differential chemical shifts Δδ(N) are defined as δ~N~(amine)‐δ~N~(enamine). This parameter is shown to correlate well with the free enthalpy of activation Δ__G__# for restricted rotation about the NC(α) bond in enamines with extended conjugation. Δδ(N) values of substituted anilinostyrenes correlate also with ^13^C‐chemical shifts of the β‐carbon in the enamine system and with Hammett σ‐constants of the aniline substituents. The experimental results suggest that differential ^15^N shifts are a useful probe to study n, π‐interaction in enamines.

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