Chemistry Letters, Vol.35, No.4, 408-409, 2006
Three-step alpha-acylation of (E)-cinnamate esters with inversion of stereochemistry through formation and cleavage of carbon-pentamethylcyclopentadienyl bonds
The reaction of cinnamate esters with lithium pentamethylcyclopentadienide in the presence of chlorodiethylaluminum provides the corresponding 1,4-adducts in high yield. The adducts undergo alpha-acylation reaction upon treatment with lithium diisopropylamide and acid chlorides. Removal of the pentamethylcyclopentadienyl group by the action of base affords alpha-acylcinnamate esters, in which the aryl and alkoxycarbonyl groups are in cis relationship.