Enantioselectivity in the Iridium-Catalyzed Hydrogenation of Unfunctionalized Olefins

The iridium catalyzed asymmetric hydrogenation of largely unfunctionalized olefins has been studied by DFT calculations using a full experimentally tested combination of ligand and substrate All possible diastereomeric pathways were considered within four different hydrogenation mechanisms The effect of a solvent continuum was also considered and both the gas phase and solvent continuum calculations favored the same mechanism This mechanism passed through Ir-III and Ir-V intermediates and was consistent with the sense of stereoselection observed experimentally Comparing the calculations to those performed on a model system permitted an evaluation of the model system s utility in representing the full one A simple general method for predicting the sense of stereoselection in iridium-catalyzed olefin hydrogenation was developed and tested against published data