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E, Z isomerization studies of ethyl 2-oxo-3-indolinylidenecyanoacetates by 1H NMR spectroscopy

✍ Scribed by Martha S. Morales-Rios; Yolanda Mora-Pérez; Pedro Joseph-Nathan

Publisher
John Wiley and Sons
Year
1992
Tongue
English
Weight
474 KB
Volume
30
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The kinetics of base‐catalysed E/Z isomerization for a series of ethyl 2‐oxo‐3‐indolinylidenecyanoacetates in CDCl~3~ solutions were studied by ^1^H NMR spectroscopy. Both polarizable double bond considerations and steric requirements of the base must be considered in explaining the results. The E/Z equilibrium of ethyl 1‐carbethoxy‐2‐oxo‐3‐indolinylidenecyanoacetate was reached faster than those of ethyl 2‐oxo‐3‐indolinylidenecyanoacetate and the 1‐methyl derivative by a factor of ca. 10 in the presence of triethylamine, and the isomerizations were faster when quinuclidine was used. In pure DMSO‐d~6~ solutions, the equilibria were established upon dissolution, but addition of small amounts of acid slowed the isomerization process in these systems.

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