Premium
E , Z isomerization studies of ethyl 2‐oxo‐3‐indolinylidenecyanoacetates by 1 H NMR spectroscopy
Author(s) -
MoralesRios Martha S.,
MoraPérez Yolanda,
JosephNathan Pedro
Publication year - 1992
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260301202
Subject(s) - chemistry , isomerization , quinuclidine , steric effects , nuclear magnetic resonance spectroscopy , medicinal chemistry , triethylamine , spectroscopy , proton nmr , kinetics , stereochemistry , computational chemistry , photochemistry , organic chemistry , catalysis , physics , quantum mechanics
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.