A straightforward approach to 2-azetidinones from imines and carboxylic acids using dimethyl sulfoxide and acetic anhydride

The direct synthesis of 2-azetidinones from imines and carboxylic acids under mild conditions is developed. Dimethyl sulfoxide (DMSO) can be activated by acetic anhydride and the resulting active species is used for the in situ generation of ketenes from carboxylic acids. This method is cheap, simple, convenient, and efficient and the products are easily isolated.