Studies in ferrocene derivatives. Part XIII. Synthesis and rearrangement of ferrocenylbicyclopropyls

Abstract

The synthesis of a number of substituted cyclopropyl ferrocenyl ketones is described. The conversion of these into dibromo(ferrocenyl)bicyclopropyls via the Wittig olefination procedure followed by addition of dibromocarbene proved more complex than expected. The bicyclopropyls from 2-phenylcyclopropyl and 2-p-methoxyphenylcyclopropyl ferrocenyl ketones were obtained as diastereoisomeric mixtures which could be separated by chromatography. The bicyclopropyl from cyclopropyl ferrocenyl ketone underwent thermal rearrangement to 2,6-dibromo-3-ferrocenylhexa-1,3-diene. Another example of this rearrangement was found during the attempted formation of a bicyclopropyl from 1-cyclopropyl-1-ferrocenylpropene.