Tricarbonyl(h6-Arene)Chromium(0) Complexes as Chiral Auxiliaries: Asymmetric Synthesis of b-Lactones

The optically pure tricarbonyl(h6-2-substituted benzaldehydes)chromium are used as chiral auxiliaries in the condensation with a series of doubly lithiated carboxylic acids. The intramolecular ring closure of the obtained Cr(CO)3 complexed b-hydroxyacids affords the optically pure b-lactones in satisfactory yield.