Enantioselective Synthesis of β-Lactones

Significance

An aluminum-catalyzed enantio­selective [2+2] cycloaddition of ketenes and aldehydes provides a practical synthesis of enantio­enriched β-lactones. The Al source is either DIBAL-H or Et₃Al and the ligand is either a di­phenyl or a dicyclohexyldiamine. Both α-branched and α-unbranched aldehydes are compatible with the reaction conditions, producing β-lactones in high yields and moderate to good ee values.