Transition-Metal-Catalyzed, Site- and Enantioselective Oxygen and Nitrogen Transfer Enabled by Lactam Hydrogen Bonds

A chiral lactam hydrogen bonding site has been employed to exert control over a series of transition-metal-catalyzed reactions in a highly enantioselective fashion. Similar to the mode of action of natural enzymes, the active site of these catalysts is covalently linked via a ligand to a chiral molecular recognition site. Along these lines, substrates decorated with a suitable binding site are aligned in a confined position whereupon considerable enantioface and site differentiation is introduced. Typical catalysts involved in these transformations include metal porphyrins, rhodium carboxylates, silver phenanthroline complexes, and ruthenium complexes with an additional chiral pybox ligand that operates synergistically. Encouraged by seminal work on the enantioselective addition to olefins (epoxidation, aziridination), the scope was later expanded to the direct functionalization of aliphatic C-H bonds (oxygenation, amination) and to enantioselective sulfoxidation reactions.