Research

Reactions developed in the Mazet group are equally methodology-driven and target-oriented. On one hand, the challenges associated with novel reactivity and selectivity often stimulates the interest for a given transformation. On the other hand, our selection of (asymmetric) target reactions is guided by the objective of synthesizing molecules that could serve as versatile building blocks. Hence, accessing structural motifs that are highly prevalent in synthesis but which – paradoxically – lack general preparation methods, provides a strong stimulus to our research program. In this context, we place a particular emphasis on asymmetric catalysis, driven by the devise of new reactivity patterns and unprecedented reaction mechanisms.

Owing to their high synthetic potential, their biological properties and the inherent challenges associated with their stereoselective preparation, chiral aldehydes are particularly attractive targets. A large part of our program consists in establishing complementary stereoselective strategies to streamline access to chiral aldehydes possessing tertiary and quaternary centers at vicinal (α, β) or remote (γ, ε…) positions. To this end, cross-couplings and redox-economical isomerizations have been elected as methods of choice in our group.
 

Isomerizations


In essence, catalytic isomerization reactions are ideal transformations as they allow complete refunctionalization of a given substrate upon an internal redox process and usually do not require the use of expensive and potentially toxic reagents and additives. The isomerizations developed in our group rely on the use of well-defined, highly reactive, late transition metal hydride complexes (Ru–H, Rh–H, Ir–H, Pd–H, Cu–H…). This original approach offers novel reactivity patterns to be explored and has so far enabled at least to complement and often to outperform most of the existing alternatives.


Cross-couplings


Due to their modular nature, cross-couplings are direct bond forming processes which allow rapid increase in molecular complexity as well as chemical diversification in a simple operation. These methods are often used in our group to complement isomerizations and in particular to forge quaternary (stereo) centers.


Ligand and Catalyst Design


Despite the arsenal of chiral ligands available to the synthetic chemist the ultimate goal for rational catalyst design is still far from reach. Therefore, there is a continuous need for the synthesis of original ligand and catalyst architectures.


Supporting Organometallic Chemistry and Mechanistic Investigations


Although the use of modern high-throughput methods is likely to contribute to accelerate discovery in catalysis, we prefer to rely on the understanding of the fundamental mechanistic aspects of the reactions we are devising. To this end, state-of-the-art physical-organic chemistry tools are used to glean insight into the nature and the fate of the intermediates that govern all aspects of reactivity and selectivity. Furthermore, supporting organometallic chemistry at the stoichiometric level often provides important information and, therefore, in a more general context, we favor catalysis using well-defined complexes over in situ catalysis.

Recent achievements in mechanistic studies include: (i) the delineation of the elementary steps of the [Ir–H]-catalyzed enantioselective isomerization of primary allylic alcohols and a rationale that accounts for the high enantioselectivities achieved; (ii) the observation of reversible oxidative addition of chiral [(P,N)Pd] complexes into aryl-bromide bonds during the asymmetric α-arylation of aldehydes; (iii) the discovery of a [Pd–H]-catalyzed isomerization of epoxides and the identification of a mechanism characterized by two distinct enantio-determining steps using a combined experimental and theoretical approach (DFT calculations).