The synthesis of a large number of β- and β,β-substituted keto esters was successful by the use of the Knoevenagel condensation reaction. The stereoselectivity of these reactions was improved by alteration of various substituent groups. Although there were few examples of complete Z selectivity, the use of tert-butyl acetoacetate with either aromatic or aliphatic aldehydes afforded Z selectivity. The selective reductions of these substituted keto esters was successfully achieved by using a combination of NaBH4 and CeCl3·7H2O or Yb(OTf)3, which allowed a facile synthesis of a large number of stereochemically pure substituted Morita–Baylis–Hillman adducts, including β,β-substituted adducts.
PCl3-mediated transesterification and aminolysis of tert-butyl esters via acid chloride formation