Fig. 3. Experimental and computational data related to the Michael addition catalyzed by UPy 2 and K₂CO₃. (a) Schematic depiction of the UPy 2 catalyzed Michael addition between Mal_ref3 and Pent_ref4. (b) Conversion of the Michael addition between Mal_ref3 (c = 4 mM) and Pent_ref4 (c = 4 mM) in the presence of K₂CO₃ (c = 36 mM) and various amounts of UPy 2 in CDCl₃ at room temperature (symbols), and the best fits of the kinetic model based on mass action kinetics of UPy catalysis through diUPy·K₂CO₃ complex formation, autocatalysis by product·K₂CO₃ complex formation, and autoinduction as a result of the product binding and further activation of the catalytically active diUPy·K₂CO₃ complex (lines). All components were combined simultaneously. (c) Conversion of the Michael addition between Mal_ref3 (c = 4 mM) and Pent_ref4 (c = 4 mM) in the presence of K₂CO₃ (c = 36 mM), in the presence of UPy 2 (c = 10 mM), or when both are present (symbols) and the best fits based on the same kinetic model as in (b) (lines). Typically, all components were combined simultaneously, except for the “premixed” measurement where UPy 2 was stirred in a suspension of K₂CO₃ in CDCl₃ for six days prior to adding the Michael substrates. (d) ¹H NMR spectra of UPy 2 (c = 4 mM) in the presence of K₂CO₃ (c = 36 mM) in CDCl₃, displaying the changes in the ¹H NMR signals corresponding to the UPy NH protons over time and their recovery upon the addition of K⁺ complexing agent 18-crown-6 (c = 8 mM). (e) Optimized geometry of the UPy–UPy dimer complexing K₂CO₃ as obtained from DFT calculations. Note that the ester moieties of the UPys fold back over the dimer plane to coordinate to the K⁺ ions. (f) Conversion of the Michael addition between Mal_ref3 (c = 4 mM) and Pent_ref4 (c = 4 mM) in the presence of K₂CO₃ (c = 36 mM) and additional Michael product (c = 10 mM) and/or UPy 2 (10 mM) in CDCl₃ at room temperature (symbols) and the best fits based on the same kinetic model as in (b) (lines). (g) Optimized geometry of the diUPy·product·K₂CO₃ complex as obtained from DFT calculations. (h) Schematic of the kinetic mass action model including the background reaction, autocatalysis, diUPy·K₂CO₃ complexation, and autoinduction. The formation of the product·K₂CO₃ complex was not included in the model as it is not required to obtain a proper fit of the data, instead its formation is viewed as being instantaneous. (i) Catalytic contributions of the background reaction, autocatalysis, UPy catalysis, and autoinduction in the Michael addition catalyzed by K₂CO₃ (c = 36 mM), Mal_ref3 (c = 4 mM), Pent_ref4 (c = 4 mM) and UPy 2 (c = 10 mM), simulated using the optimized parameters.