Tunable ferrocenyl diphosphine ligands for the Ir-catalyzed enantioselective hydrogenation of N-aryl imines

Enantioselective Hydrogenation of Trimethylindolenine in Ionic Liquids

“…al. [6] Now, only the catalyst components (iridium source, ligand) and the promoters (acid, TBAI) were added and given time (1 h) to form the active precatalyst (we later found that 0.5 h formation time was also sufficient). The substrate was added directly before …”

“…[6] To judge the effects of the ionic liquid, a variety of ionic liquids with different physicochemical properties was synthesized according to known literature procedures [7 ± 9] with slight modifications where necessary. Our ™ionic liquid construction kit∫ consists of three basic building blocks that, taken together, form the ionic liquid: (a) the cation, (b) the substituent in the cation, and (c) the anion (cf.…”

“…al. [6] are shown in Table 1. The only difference to the literature was that our reaction mixture came shortly into contact with air while transferring it into the autoclave.…”

Enantioselective Synthesis of Alcohols and Amines by Iridium‐Catalyzed Hydrogenation, Transfer Hydrogenation, and Related Processes

“…[25] Likewise, the use of 3,4,5,6-tetrafluorophthalimide as an additive in combination with Ir-(R)-BINAP ((R)-24) had a positive influence on activity and selectivity (Scheme 6). [26] This system was used in the synthesis of alkaloid (S)-calyctomine (28), in which the key step, hydrogenation of imine 13 b, was achieved in 85 % yield with an ee of 86 %.…”

“…Although similar levels of enantioselectivity were obtained, none of the new ligands gave comparable activity to that obtained with the Xyliphos (1 a) system in the reduction of the industrial target MEA imine (2 a). [28] The screening showed that ferrocenyl diphosphine ligands are substrate specific, and to obtain high ee values the optimal ligand (1 a-e) and reaction conditions had to be varied for each substrate (Scheme 7). Subsequently, the same group prepared an immobilized version of Ir-Xyliphos.…”