Salts as building blocks for organocatalysis

A molecule and its twin

There are certain molecules that exist twice, so to speak: as themselves and as their mirror image. “These so-called chiral molecules demonstrate a handedness of sorts,” explains Stefan Huber. Despite sharing many similarities, they have very different properties, for example in terms of their biological effectiveness. When used as a component of medicines, for example, the original molecule can have the desired effect, while its mirror image can cause adverse effects. This is why the aim is usually to produce only one variant of the molecule. 

To this end, the team from Bochum and Mülheim adopted a novel approach. Their aim was to produce a molecule with interesting properties for medical application. The researchers used salts as catalysts in which both components (cation and anion) play an important role: The cation sets the reaction in motion via halogen bonds. “Halogen bonds are weak bonds formed between the cation and the substrate,” explains Dominik Reinhard, PhD student from Bochum. For its part, the anion, produced by the Mülheim researchers, ensures the correct handedness of the resultant molecule. 

“The salt is introduced to the relevant substrates in a compatible solvent. The concerted action of the salt components then ensures the desired reaction, during which only the molecule with the desired handedness is formed,” explains Dominik Reinhard. 

“What makes this approach so attractive is that, by using salts, we’ve created a modular system,” points out Stefan Huber. By combining a wide range of different cations and anions, the researchers can thus create different salts and, consequently, catalyze different reactions going forward.