Iridium-Catalyzed Asymmetric Hydrogenation of Fluorinated Olefins Using N,P-Ligands:  A Struggle with Hydrogenolysis and Selectivity

• Published in: Journal of the American Chemical Society Vol. 129; no. 15; pp. 4536 - 4537
• Main Authors: Engman, Mattias, Diesen, Jarle S, Paptchikhine, Alexander, Andersson, Pher G
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 18.04.2007; Amer Chemical Soc
• Subjects: Alkenes - chemical synthesis; Alkenes - chemistry; Catalysis; Chemistry; Chemistry, Multidisciplinary; Fluorine - chemistry; Hydrogen - chemistry; Iridium - chemistry; Kemi; Ligands; Molecular Structure; NATURAL SCIENCES; NATURVETENSKAP; Physical Sciences; Science & Technology; Stereoisomerism; CHEMISTRY; OXAZOLINE LIGANDS; JM-PHOS LIGANDS; ENANTIOSELECTIVE HYDROGENATION; COMPLEXES
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/ja0686763

To broaden the substrate scope of asymmetric iridium-catalyzed hydrogenation, fluorine-functionalized olefins were synthesized and hydrogenated with iridium complexes. Preliminary results showed high levels of fluorine elimination together with low selectivity. The loss of vinylic fluorine at first seemed difficult to handle, but further studies revealed that a catalyst with an azanorbornyl scaffold in the ligand gave more promising results. With this in mind, a new ligand was developed. This gave among the best results published to date for fluorine asymmetric hydrogenation, yielding high conversion and very high ee's with very little fluorine elimination. Further increasing the selectivity, the trials also revealed that tetrasubstituted fluorine-containing olefins can be hydrogenated with high ee's, despite that this class of compounds has usually shown low reactivity in this reaction type.