Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd−Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.

Stereoselectivity in heterogeneous hydrogenation of olefins and arenes is typically dictated by the steric properties of the organic substrate, and the inherent steric preference is difficult to alter through the modification of the catalyst or experimental parameters. One strategy to access counter-steric selectivity is to incorporate a stereochemically defined functional group into the substrate that can adsorb to the catalyst surface and “direct” hydrogen addition from the same face. This Perspective provides an overview of heterogeneous directed hydrogenation and elucidates a few design rules about directing group identity, substrate structure, and catalyst composition that lead to diastereoselective reactivity. Monometallic heterogeneous catalysts are capable of diastereoselective directed hydrogenation with only a limited set of substrate scaffolds and directing functional groups. In a given substrate, the complex interplay between directing group conformation, steric bulk, and adsorption strength makes it difficult to predict whether steric or electronic factors will dominate the diastereoselectivity. We then discuss more recent examples of bimetallic catalysts for this reaction and look toward opportunities for bimetallic structures to yield more tunable and general heterogeneous directed hydrogenation catalysts.

3-Aryl-1-phosphinoimidazo[1,5-a]pyridine ligands were synthesized from 2-aminomethylpyridine as the initial substrate via two complementary routes and were evaluated in the Suzuki–Miyaura cross-coupling reactions.

3-Aryl-2-phosphoimidazo[1,2-a]pyridine ligands were prepared via two complimentary synthetic routes and were evaluated in the Suzuki–Miyaura and Buchwald–Hartwig amination cross-coupling reactions.