E,Z isomerization studies of ethyl 2-oxo-3-indolinylidenecyanoacetates by1H NMR spectroscopy
作者:Martha S. Morales-Rios、Yolanda Mora-Pérez、Pedro Joseph-Nathan
DOI:10.1002/mrc.1260301202
日期:1992.12
The kinetics of base-catalysed E/Z isomerization for a series of ethyl 2-oxo-3-indolinylidenecyanoacetates in CDCl3 solutions were studied by 1H 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-d6 solutions, the equilibria were established upon dissolution, but addition of small amounts of acid slowed the isomerization process in these systems.
通过 1H NMR 光谱法研究了一系列 2-oxo-3-indolinylidenecyanoacetates 乙酯在 CDCl3 溶液中碱催化 E/Z 异构化的动力学。在解释这些结果时,必须同时考虑可极化双键因素和碱的立体要求。在三乙胺存在下,1-乙氧羰基-2-氧代-3-吲哚啉亚癸氰基乙酸乙酯的 E/Z 平衡比 2-氧代-3-吲哚啉亚癸氰基乙酸乙酯和 1-甲基衍生物的 E/Z 平衡快约 10 倍,而使用奎宁环时,异构化速度更快。在纯 DMSO-d6 溶液中,溶解后即可建立平衡,但在这些体系中加入少量酸会减缓异构化过程。