Exploiting Poly-Lewis Acids for Controlled, Catalytic Semi-Reduction – a Main Group Solution for an Unmet Synthetic Need

• Applicant: Dr. Lucas Marvin Kistner
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572959415

The selective semi-reduction of esters and carboxylic acid derivatives to aldehydes remains an unmet synthetic challenge. More often than not a two-step reaction pathway is used consisting of “over-”reduction to the corresponding alcohol and then oxidation to the aldehyde. Even using state-of-the art transition metal catalysis the alcohol is often obtained as a by-product and functional group tolerance remains limited, ignoring the toxicity or CO2 footprints of using such metals. This Fellowship will develop novel poly-Lewis acid catalysts for the chemoselective semi-reduction of esters to aldehydes. The poly-Lewis acids will be based on sustainable main-group elements; boron and aluminum. The poly-Lewis acid structure will act to: 1. Abstract a hydride from a suitable hydride source (e.g. boranes, silanes, etc.); 2. Recognize the ester substrate through a bidentate Lewis acid-Lewis base interaction; 3. Transfer the hydride to the ester substrate; 4. Bind the reduced reaction intermediate to prevent over-reduction. The catalytic cycle will undergo turnover by metathesis with the (main group) hydride source to release the product as a stable hetero-acetal. After aqueous work-up the aldehyde will be obtained. By developing a library of different poly-Lewis acids in combination with various hydride sources, the catalysts can be precisely adapted to the requirements of the substrates and make the hitherto difficult semi-reduction generally possible, with high functional group tolerance.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Dr. Stephen Thomas, Ph.D.