Azomethineimines. V. 1H‐N.M.R. Spectra and Steric Properties of Arylsubstituted Pyrazolidone‐Azomethineimines
From the results of 1H‐n.m.r.‐spectroscopic investigations we tried to draw conclusions regarding the steric properties of pyrazolidone‐azomethineimines 1a–k. The influence of aromatic systems on chemical shift of the methineproton of the 1,3‐dipolar centre was calculated using the ring current model. Without the twisted 9‐anthryl‐substituted compound 1f experimental results show a good correspondence to the values of chemical shift calculated for two of four possible isomeric structures.
Reaction of α‐Cyano‐β‐aryl Acrylic Acid Ethylesters with Hydrazine, a Retro‐Knoevenagel‐Reaction
We tried to obtain 4‐cyano 5‐aryl pyrazolidones‐(3) 3a, b and related azomethine imines 4a, b. However the reaction of α‐cyano β‐aryl acrylic acid ethylesters 2a, b with hydrazine yields the familiar cyano acetic acid arylidene hydrazides 5a, b by cleavage of the carbon‐carbon double bond. 5a, b react with pyrene‐1‐aldehyde to 7a, b. Formation of 5a, b is proved by an independent synthesis. 5a, b and 7a, b are investigated by mass spectrometry.
Durch Kondensation des Cyanessigesters (I) mit den aromatischen Aldehyden (II) werden nach literaturbekanntem Verfahren die Cyanacrylsäureester (III) dargestellt.
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