Kinetic Profiles as a Diagnostic Probe of Complex Multi-Cycle Catalytic Reaction Networks

Many high-profile catalytic reactions in modern organic synthesis involve coupled multicycle networks, with key examples including organocatalytic cascade reactions and photochemical and electrochemical systems. Distinct catalytic cycles combine to operate as connected "cogs" within the overall reaction network. In these cases, one cycle may produce a product that is subsequently delivered as a substrate to a second cycle, and one or more catalytic intermediate species may be shared between multiple catalytic cycles. Such complex systems exhibit features that are not easily interpreted by conventional kinetic and mechanistic analyses that focus on individual elementary reaction steps─or even individual catalytic cycles─in isolation from the full network. Competition for the catalyst between different components in different cycles may result in unexpected trends in overall productivity, reflected in observations of unusual substrate concentration dependences, rate laws, and catalyst speciation. In this work, reaction network simulations are carried out based on selected examples of complex organocatalytic and electrocatalytic reactions to illustrate how kinetic profiles may help to address the challenge to understand, predict, and optimize outcomes in complex, connected, multicycle systems.