Computational study on the pKa shifts in proline induced by hydrogen-bond-donating cocatalysts
Xiao-Song Xue1, Chen Yang, Xin Li
1State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Department of Chemistry, Nankai University , Tianjin 300071, China.
Abstract:
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 pKa 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 pKa shifts of proline in the gas phase and common organic solvents were established and were found to be well-correlated 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.
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