Iridium-Catalyzed Asymmetric Hydrogenation of Olefins

Abstract

Asymmetric hydrogenation is one of the most important catalytic methods for the preparation of optically active compounds. For a long time the range of olefins that could be hydrogenated with high enantiomeric excess was limited to substrates bearing a coordinating group next to the C+C bond. We have found a new class of catalysts, iridium complexes with chiral P, N ligands, that overcome these limitations. For a wide range of unfunctionalized olefins, excellent enantioselectivities could be achieved. Because these catalysts do not require the presence of any particular functional group in the substrate, they considerably broaden the scope of asymmetric hydrogenation. In addition, promising results were also obtained with certain functionalized alkenes, furans, and benzofurans.

Asymmetric Hydrogenation

“…These successful results have significantly adv a n c e d t h i s a r e a o f r e s e a r c h w i t h t h e development of numerous chiral P,N-ligands [13,[54][55][56][57][58]. Representatives of the chiral iridium complexes so far reported are shown in Fig.…”

New Catalytic Asymmetric Strategies to Access Chiral Aldehydes

“…The corresponding air-stable [(PN) Ir(cod)].BAr F complexes were obtained in good yields (60-88%) following literature procedures (Scheme 2). [11] Preliminary investigations on a model substrate showed that (i) these complexes displayed a catalytic activity similar to the achiral catalyst 1, (ii) the reaction was highly dependent on the size of the P-alkyl substituents; the bulkier substituents leading to the highest enantioselectivities. Under the optimized conditions, the isomerization product was obtained with unprecedented yield and enantioselectivity (98% yield, 95% ee or 75% yield, 97% ee).…”

Iridium‐Catalyzed Asymmetric Hydrogenation of Substituted Pyridines

“…4 More recently, homogeneous iridium catalysed asymmetric hydrogenation allows, through excellent enantio-selectivity and atom economy, the efficient synthesis of chiral compounds, especially building blocks. 5 After Pfaltz' improvement on Crabtree's catalyst, methods of iridium catalyzed asymmetric hydrogenation were developed extensively. 6 These new catalysts were obtained by replacing the previously used PF 6…”