Asymmetric transfer hydrogenation of prochiral cyclic 1,3-diketones

The enantioselective mono reduction of 2,2-dimethylcyclopentane-1,3-dione and 2,2-dimethylcyclohexane-1,3-dione was investigated.From the ruthenium, rhodium, and iridium TsDPEN complexes screened with isopropanol or formic acid as the hydrogen donor, the ruthenium complex performed best for both substrates.The resulting hydroxy ketones 3-hydroxy-2,2-dimethylcyclopentanone and 3-hydroxy-2,2dimethylcyclohexanone, which are important building blocks for natural product synthesis, were obtained in excellent yield with high enantiomeric excess.