“…Homogeneous alkene hydrogenation catalysts, unlike their heterogeneous counterparts, offer the opportunity to promote site selective reactions through rational ligand design . Among these, directed hydrogenations where the interaction of a functional group in the substrate with the catalyst imparts high levels of stereocontrol have found widespread application in synthesis due to the ability to access products with contrasteric selectivity. − Wilkinson’s, Schrock–Osborn-type, and Crabtree’s catalysts, (Ph 3 P) 3 RhCl, [(P–P)Rh(COD)] + , and [Ir(COD)(py)(PCy 3 )] + (COD = 1,5-cyclooctadiene, py = pyridine, Cy = cyclohexyl), respectively, have been the most widely used due to their high activity, selectivity, ease of handling, and availability.…”