Computational Study on the pK_a Shifts in Proline Induced by Hydrogen-Bond-Donating Cocatalysts

摘要

The pKa shifts of proline induced by a family of hydrogen-bond-donating cocatalysts were computationally evaluated with the M06-2x/6-311++G(2df, 2p)//B3LYP/6-31+G(d)(SMD) method. The calculation predicted that the acidity of proline could be increased by more than 9 pK_a units in nonpolar solvents (n-hexane and toluene) when it assembles with hydrogen-bond-donating cocatalysts, which would contribute to the dramatically enhanced catalytic properties. For hydrogen-bond-donating cocatalysts, their relative abilities to induce the pK_a shifts of proline in the gas phase and common organic solvents were established and were found to be wellcorrelated with their acidities. The results may aid in future development of modularly designed supramolecular catalysis-the assembly of catalyst species by harnessing multiple weak intermolecular interactions.