Oximes of Terpenoid Ketones and Their Analogs

The first syntheses of pyrroles bearing unsaturated substituents from y,6-ethylenic ketones have been reported in works [207,208]. It is shown that oximes of these ketones easily react with acetylene to form the expected alkenylpyrroles in good or moderate yields. 

SCHEME 1.36 Synthesis of pyrroles from oximes of y,5-ethylenic ketones. 

Later on, the structural effects of the alkenyl group of terpenoid ketone (5-alken-2-ones) oximes on the formation of pyrroles and N-vinylpyrroles as well as on prototropic isomerization of the alkenyl substituent have been studied [209]. 

SCHEME 1.39 Prototropic isomerization of alkenyl substituents in pyrroles and N-vinylpyrroles in the KOH/DMSO and f-BuOK/DMSO systems. 

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