CNRS Science news Chemistry: Catalysts with switchable selectivity

Most chiral molecule syntheses produce several molecules called isomers, with the same chemical formula, but which do not overlap in 3 dimensions. For many applications, it is necessary to produce them separately, as they sometimes have very different properties. Scientists at the CNRS have developed a unique catalyst capable of synthesizing each isomer of a chiral molecule preferentially.

Helical supramolecular structure providing access to the four isomers of the amino-alcohol shown in the box. © Matthieu Raynal

Like our hands, chiral molecules exist in two forms called enantiomers, with the same chemical formula, but whose structures are mirror images of each other and not superimposable. Two enantiomers can have completely different properties despite their apparent similarity.

Most syntheses of chiral molecules produce a mixture of the two enantiomers. For many applications, notably in pharmaceutical chemistry or materials, it is therefore necessary to separate them or to develop ways of synthesizing them selectively.

To direct the production of one isomer rather than the other, chemists have developed numerous organometallic catalysts. However, synthetic methodologies for accessing each isomer of a chiral molecule remain limited, requiring numerous catalysts involving complex chemical processes that are still poorly understood. What if a single catalyst made it possible to obtain each isomer of a chiral molecule independently?

Scientists at the Paris Institute of Molecular Chemistry (CNRS/Sorbonne University) have just achieved this by creating a chiral helical supramolecular structure in which a copper atom forms the catalytic site. By playing on the chemical nature of the molecular entities that make up the catalyst, they have succeeded in controlling the direction of rotation of its helices and thus the nature of the isomer obtained. Better still, they can modify the catalyst in situ by changing the direction of rotation of the helix, which amounts to switching the selectivity of the catalyst during the reaction.

This selectivity, tested on the synthesis of a chiral amino alcohol, enabled high enantiomeric excesses (≥ 93%) to be obtained, with or without selectivity switching. A first step towards efficient catalysts for rapid access to all isomers of a molecule of interest, to be found in the journal Nature Communications.

Reference

Ran Chen, Ahmad Hammoud, Paméla Aoun, Mayte A. Martínez-Aguirre, Nicolas Vanthuyne, Régina Maruchenko, Patrick Brocorens, Laurent Bouteiller, & Matthieu Raynal

Asymmetric stereodivergent catalysis achieved by means of a switchable asymmetric catalyst built on supramolecular helices

Nature Communications, 2024, 15, 4116

https://doi.org/10.1038/s41467-024-48412-z

Contact: Matthieu Raynal