Enantioselective hydrogenation of trimethylindolenine in ionic liquids

The enantioselective hydrogenation of trimethylindolenine (1) has been carried out in a variety of ionic liquids using an Ir-XYLIPHOS catalyst. Compared to the reaction in conventional organic media, slightly higher temperatures (50degreesC) are required, which is mainly due to the higher viscosities of the ionic media. Under these conditions we were able to identify three reaction media that gave ees comparable to the conventional process in toluene with greatly reduced reaction time (15 h as opposed to 23 h for 100% conversion; 91% conversion after 8 h). The sensitivity of the reaction system towards oxygen was also reduced significantly.