Stereochemical issues on the fragmentation of non-enolisable β-heterosubstituted-cyclopentanones with wet and anhydrous potassium hydroxide

Tandem Haller-Bauer-scission/Grob-fragmentation reaction of cyclopentanone bearing a leaving group in β-position involves antiperiplanar arrangements which can be also achieved from epimeric derivatives, probably due to the high flexibility of the five-membered ring. We have observed that epimeric compounds react at different rates if the leaving group is a halogen and leads to very different types of compounds when it is a mesyl group.