The use of modern catalytic methods, such as enantioselective hydrogenation in multi-hundred metric ton scale, still offers many challenges and is accordingly relatively rare. A robust and economical process demands identification of the right catalytic system and conditions that allow for full conversion and high stereo- and chemoselectivity at very low catalyst loadings. Crabtree/Pfaltz-Type iridium complexes are one of the very few options to achieve high enantioselectivity in the hydrogenation of non-functionalized olefins. However, the high price of iridium demands substrate to catalyst ratios in the order of 10000:1 for attractive use cases in CropScience, which has been out of reach so far. In search of a new production process for the novel fungicide Inpyrfluxam, we identified a single promising Crabtree/Pfaltz-Type Iridium complex using plate screening technology. Though only 25 turnovers were achieved initially, our labs succeeded in increasing this number to &gt;10000 turnovers in collaboration with partners in both industry and academia. Moreover, we achieved not only excellent enantioselectivities of &gt;97% ee, but also very attractive space-time yields. Research activities included optimizing reaction solvent, additives, conditions, as well as the catalyst structure itself. The presentation will give a detailed account of this development journey and furthermore describe the large-scale preparation procedure of the chiral ligand backbone of catalyst SSCH1049.

Industrial-scale enantioselective hydrogenation using Pfaltz-type catalysts: Chemical development and academic collaborations

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