Energy Decomposition Analysis Reveals the Nature of Lone Pair-π Interactions with Cationic π Systems in Catalytic Acyl Transfer Reactions.

Lone pair-π (LP-π) interactions between Lewis basic heteroatoms, such as oxygen and sulfur, and electron-deficient π systems are important noncovalent interactions. However, they have seldom been used to control catalyst-substrate interactions in catalysis. We performed density functional theory calculations to investigate the strengths of LP-π interactions between different lone pair donors and cationic π systems, and in different complexation geometries. Energy decomposition analysis calculations indicated that the dominant stabilizing force in LP-π complexes is electrostatic interaction and the electrostatic potential surface of the π system predicts the most favorable site for forming LP-π complexes. Benzotetramisole (BTM) is revealed as a privileged acyl transfer catalyst that promotes LP-π interactions because the positive charge of the acylated BTM is delocalized onto the dihydroimidazole ring, which binds strongly with a variety of oxygen and sulfur lone pair donors.