. "with an ??-haloester HalCH2CO2Alk4 [where Hal is a halogen atom such as a bromine atom] in the presence of a strong base, e.g. a silazide such as sodium or lithium hexamethyldisilazide in a solvent such as an ether, e.g. a cyclic ether such as tetrahydrofuran at a low temperature, e.g. around ???78??? C." . . .