Unexpected Isomerization of Oxetane-Carboxylic Acids

Many oxetane-carboxylic acids were found to be unstable. They easily isomerized into new (hetero)cyclic lactones while being stored at room temperature or slightly heated. Chemists should keep in mind the high instability of these molecules, as this could dramatically affect the reaction yields and lead to negative results (especially in those reactions that require heating).