The Hydrolysis of the Anhydride of 2‐Cyano‐2‐phenylpropanoic Acid Triggers the Repeated Back and Forth Motions of an Acid–Base Operated Molecular Switch

This work aimed to render phenomenologically autonomous the otherwise stepwise operation of a catenane-based molecular switch, which is chemically triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid (2). Given that any amount of 2 in stoichiometric excess with respect to the catenane is consumed in a side reaction, the authors resorted to the corresponding anhydride 5, the slow hydrolysis of which, due to adventitious water in dichloromethane, continuously produces in situ the actual fuel 2. As a consequence, the machine does not require a reloading after each cycle, but switches back and forth as long as fuel is present.