Iridium Catalyzed Asymmetric Hydrogenation of 5‐Methylene‐Benzosuberanes

Asymmetric hydrogenation of 5‐methylene‐benzosuberanes using iridium‐PHOX catalysts is reported. While the P‐stereogenic ligand PepPHOX‐ t Bu afforded an unprecedented 92% ee for the parent substrate, competitive isomerization was found to erode selectivity. Investigation of catalyst structure–activity relationships enabled the rational design of Ir–NoaPHOX , a novel catalyst engineered to suppress this undesired isomerization pathway. Because its selectivity is independent of reaction pressure, the Ir–NoaPHOX catalyst enables efficient hydrogenation under low‐pressure conditions. A range of derivatives was successfully reduced using both catalytic systems: Ir–NoaPHOX for robust low‐pressure performance and Ir–PepPHOX‐ t Bu for maximum enantioselectivity working at 50 bar pressure.