Quantum chemical studies of asymmetric reactions: Historical aspects and recent examples

Abstract

Asymmetric catalysis is essential for the synthesis of chiral compounds such as pharmaceuticals, agrochemicals, fragrances, and flavors. For rational improvement of asymmetric reactions, detailed mechanistic insights are required. The usefulness of quantum mechanical (QM) studies for understanding the stereocontrol of asymmetric reactions was first demonstrated around 40 years ago, with impressive developments since then: from single-point Hartree-Fock/STO-3G calculations on small organic molecules (1970s), to the first full reaction pathway involving a metal-complex (1980s), to the beginning of the density functional theory (DFT)-area, albeit typically involving truncated models (1990s), to current state-of-the-art calculations reporting free energies of complete organometallic systems, including solvent and dispersion corrections. The combined studies show that the stereocontrol in asymmetric reactions largely is exerted by non-bonding interactions, including CH/π attraction and repulsive forces. The ability to rationalize experimental results opens up for the possibility to predict enantioselectivities or to design novel catalysts on basis of in silico results.