Diastereoselective cyclopropanation of cyclic enones with methyl dichloroacetate anion

Abstract The reaction of α,β-unsaturated cyclic ketones with methyl dichloroacetate anion in the presence of DBU leads to the corresponding bicyclic chlorocyclopropanes in a highly diastereoselective fashion. In the cases of 2-cyclopentenone and 2-cyclohexenone the reaction affords exclusively the endo -Cl isomer.