Asymmetric hydrosilylation, transfer hydrogenation and hydrogenation of ketones catalyzed by iridium complexes

Ketone Hydrogenation with Iridium Complexes with “non N–H” Ligands: The Key Role of the Strong Base

“…Interest in iridium as a catalytic metal is sparked by the observation that it outperforms rhodium for the ionic hydrogenation of particularly difficult substrates such as imines and industrial processes based on Ir-catalyzed ketone hydrogenation have been implemented. [37][38][39][40] Contrary to olefins, unsaturated oxygenated substrates may be hydrogenated by the outer sphere mechanism, 41, 42 without substrate coordination. These processes are also characterized by the need of a strong base co-catalyst in order to function.…”

Chiral β-Amino Alcohols as Ligands for the Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of N-Phosphinyl Ketimines

“…Since those ligands have shown to give excellent results in the ruthenium-catalyzed asymmetric transfer hydrogenation of ketones [12][13][14][15][16][17][18][19] and N-sulfinylimines [38][39][40][41] in isopropyl alcohol, we decided to investigate if they could also be applied to the reduction of N-phosphinyl ketimines by the same methodology. One of the most noteworthy chiral β-amino alcohols in the ATH of both ketones and N-sulfinyl imines is cis-1-amino-2-indanol [50].…”

“…The ATH protocol presents several advantages: it is operationally simple, proceeds under mild reaction conditions, generally uses low catalyst loadings and avoids the handling of hazardous chemicals such as metallic hydrides or hydrogen gas. The ATH of prochiral ketones affords enantiomerically enriched secondary alcohols with excellent results [12][13][14][15][16][17][18][19]. Nevertheless, the asymmetric reduction of iminic compounds by transfer hydrogenation yielding chiral amines still remains underdeveloped and represents a challenging objective [20,21].…”

Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

“…Interestingly, this Rhcatalyst showed preferential activity and stereoselectivity for fluorinated ketone substrates since acetophenone gave only a 2% yield of 1-phenylethanol in 8% ee. The hydrogenation of ketones catalyzed by chiral iridium complexes has been well studied and developed because iridium is less expensive than rhodium (Malacea et al, 2010). Generally, Ir(I) or Ir(III) complexes with chiral diamines, diphosphines or a combination of both, very similar to those in Ru-catalyzed hydrogenation, have been successfully employed in the AH of various aromatic ketones and -keto esters.…”