Influence of Base Strength on the Proton‐Transfer Reaction by Density Functional Theory

Abstract

DFT methods have been used to investigate base‐assisted effects on proton‐transfer reactions, including the cleavage of C–H bonds in metal‐catalyzed organic synthesis. Anion ligands (OTf–, BF4–, or SbF6–) have been shown to effectively promote cleavage of the C–H bond and then assist proton migration as a proton‐transfer shuttle. Importantly, the calculations revealed that the catalytic activity (OTf– > BF4– > SbF6–) in the C–H bond‐breaking step is controlled by the Brønsted/Lewis basicity of the anion ligand (OTf– > BF4– > SbF6–) through a hydrogen‐bonding (base···C–H) interaction. Additives play a similar role to the anion ligands, and the use of a strong base as an additive is much more effective in promoting cleavage of the C–H bond than a weak base. In short, the present study has provided a greater understanding of the effects of base strength on proton‐transfer reactions involving C–H bond cleavage and offers guidance for the future design of new catalysts and new reactions.

Optimization of Catalysts and Conditions in Gold(I) Catalysis—Counterion and Additive Effects

“…77 In these cases, therefore, counterions possessing high hydrogen bonding basicity may play an essential role in the proton transfer. 78 However, it should be noted that counterions, as good hydrogen bond acceptors, may also have a high gold affinity. Hence, the overall effectiveness of a counterion will depend on the delicate balance between its gold affinity and its hydrogen bond basicity.…”

DFT Study on the Gold(I)‐Catalyzed Dehydrogenative Heterocyclization of 2‐(1‐Alkynyl)‐2‐alken‐1‐ones to form 2,3‐Furan‐Fused Carbocycles: Effects of Additives C5H5NO vs. PhNO

“…The geometric structures of all the intermediates and the transition states are calculated with the Becke three‐parameter hybrid functional (B3LYP) in the framework of density functional theory (DFT) . This computational method has been successfully applied in the mechanistic studies of transition‐metal‐catalyzed reactions . As a further test for the functionals CAM‐B3LYP, M06, BLYP, B3P86, B3PW91 and BHandHLYP are evaluated, and their calculation results are close to those of B3LYP (see Table S1 in Supporting Information).…”

“…The double‐ζ basis set (6‐31G*) is employed for N, C, O, Cl, P and H elements, while Au element is described using the effective core potential double‐ζ basis set (LanL2DZ) . This combination of basis sets (6‐31G* and LanL2DZ) has also been proven to be reliable in numerous theoretical simulations of mechanisms of metal‐catalyzed reactions . As a further test, other basis sets 6‐31G**, 6–31 + G* and 6‐311G* (triple‐zeta) are employed for comparison to avoid the shortcomings of basis sets (see Table S2 in Supporting Information).…”

“…[35] This computational method has been successfully applied in the mechanistic studies of transition-metal-catalyzed reactions. [36][37][38][39][40][41][42][43] As a further test for the functionals CAM-B3LYP, M06, BLYP, B3P86, B3PW91 and BHandHLYP are evaluated, and their calculation results are close to those of B3LYP (see Table S1 in Supporting Information). The double-ζ basis set (6-31G*) [44][45][46] is employed for N, C, O, Cl, P and H elements, while Au element is described using the effective core potential double-ζ basis set (LanL2DZ).…”

“…[47] This combination of basis sets (6-31G* and LanL2DZ) has also been proven to be reliable in numerous theoretical simulations of mechanisms of metal-catalyzed reactions. [37,[40][41][42][48][49][50] As a further test, other basis sets 6-31G**, 6-31 + G* and 6-311G* (triple-zeta) are employed for comparison to avoid the shortcomings of basis sets (see Table S2 in Supporting Information). All stationary points are verified by frequency calculations at the same level of theory to obtain zero-point energy (no imaginary frequency for an equilibrium structure and one imaginary frequency for a transition state structure).…”