Dioximes Separated by Conjugated Systems

The assessment of application scopes of novel pyrrole synthesis has revealed [274] that it can be extended to such essentially new group of oximes as aromatic dioximes. For example, dipyrroles separated by the phenylene fragment, dipyrrolylben-zenes, can be prepared in a one-stage fashion from 1,4-diacetylbenzene dioxime. 

The behavior of 4,4 -diacetyldiphenyl dioxime under conditions typical for the previous reaction proved to be unexpected its treatment with acetylene in the systems MOH/DMSO (M=Li, K, Cs) at 100°C-150°C both at atmospheric pressure and under acetylene pressure does not lead to either the expected 0-vinyl oximes or pyrroles [275]. Instead of them, either the initial dioxime is mainly recovered or the monooxime or complex mixtures of products are formed. 

SCHEME 1.86 Synthesis of dipyrrolylbenzenes from 1,4-diacetylbenzene dioxime and acetylene in the system KOH/DMSO. 

SCHEME 1.88 Selective synthesis of mono-N-vinyl derivative of 1,4-dipyrrolebenzene in the LiOH/DMSO system. 

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