Polyketo-enols and chelates. Part III. The constitution and chemistry of the glaucophanic enols

Abstract

The glittering black compound obtained from the condensation of ethyl ethoxymethyleneacetoacetate and ethyl sodioacetoacetate is a novel pyrone-oxonol type. The structure is based on proton magnetic resonance data, which show an AMX pattern and other features characteristic of the system proposed, on other spectral evidence, and on the pattern of chemical behaviour. Thus, pyrolysis forms a pyrone, reaction with hydrazine gives a diazole, and boiling water a p-hydroxyacetophenone ester (but no ethyl acetoacetate); these are all products expected from knowledge of xanthophanic enol chemistry (preceding Paper).

On treatment with a large excess of magnesium methoxide both diethyl- and dimethyl-glaucophanic enol give the same compound, the structure of which is established by spectral information and its degradation to resorcinol derivatives and two methyl hydroxy-1,3-benzenedicarboxylates. A mechanism of formation for the compound is proposed which uses both types of alkoxide catalysed cyclisation dealt with in the case of xanthophanic enol (preceding Paper) in the one molecule. The reason for this is considered. In the case of diethyl glaucophanic enol one ester interchange is involved, probably because of the solubility of the magnesium complex. The formation of the glaucophanic enols formally involves two diacetylglutaconic ester units linked through a one carbon unit.