Fig. 4. Experimental and computational data related to the Michael addition catalyzed by K2CO3 and combinations of NaPy 1 and UPy 2. (a) Schematic depiction of the NaPy 1, UPy 2 and K2CO3 catalyzed Michael addition between Malref3 and Pentref4. Part of the UPy and NaPy will form UPy–NaPy heterodimers in solution, which are catalytically inactive. (b) The conversion of the Michael addition between Malref3 (c = 4 mM) and Pentref4 (c = 4 mM) in the presence of K2CO3 (c = 36 mM), NaPy 1 (c = 8 mM) and various amounts of UPy 2 in CDCl3 at room temperature (symbols). In addition, the best fits of the kinetic model based on mass action kinetics of NaPy, diUPy and UPy–NaPy phase-transfer catalysis, autocatalysis as a result of the Michael product functioning as an additional phase-transfer catalyst, and autoinduction caused by the Michael product binding and thereby activating the already catalytically active diUPy·K2CO3 complex (lines, see Fig. S12† for details on the kinetic model) are shown. The insets depict the speciation of UPy and NaPy at the start of each reaction and the time required to reach 50% conversion using the different equivalents of UPy 2. All reactions were performed in CDCl3 at room temperature, all components were combined simultaneously. (c) Schematic of the expanded kinetic mass action model including the background reaction, autocatalysis, diUPy·K2CO3 complexation, autoinduction, NaPy catalysis, and UPy–NaPy catalysis. The formation of product·K2CO3, diNaPy·K2CO3 and UPy–NaPy·K2CO3 complexes was not included in the model as this is not required to obtain a proper fit of the data, instead their formation is viewed as instantaneous. (d) Catalytic contributions of the background reaction, autocatalysis, UPy catalysis, UPy autoinduction, NaPy catalysis, and UPy–NaPy catalysis in the Michael addition catalyzed by K2CO3, NaPy (c = 8 mM), and UPy (c = 12 mM = 1.5 eq.), simulated using the optimized parameters of the best fit.
