CYCLOPROPYL CARBANIONS DERIVED FROM ESTERS OF 2-PHENYLCYCLOPROPYLCARBOXYLIC ACIDS: CONFIGURATIONAL STABILITY AND REACTION WITH ELECTROPHILES

Article abstract of DOI:10.1016/S0040-4020(01)91267-0

The base-catalyzed cis-trans isomerization of cis and trans-alkyl 2-phenylcyclopropylcarboxylates was studied in several aprotic solvents.It was found that contact ion-pairs of the derived carbanion lithium salts were configurationally more stable than the solvent-separated ones.Reaction of either the cis or the trans esters with Mel, and the reaction of the cis ester with Ph₂C=O, resulted in the corresponding 1-substituted derivatives having cis geometry only.This was explained as due to steric hindrance to electrophilic attack exerted by the 2-phenyl group in the case of the trans substrate.The trans esters did not react with Ph₂C=O.Inhibition of the trans-to-cis isomerization of the carbanion salt of the trans substrate in presence of Ph₂C=O could lead to this result.