Theoretical study of an anti-Markovnikov addition reaction catalyzed by β-cyclodextrin.

β-Cyclodextrin (β-CD) has a hydrophilic exterior and a hydrophobic internal cavity, which allows it to form host-guest complexes with a wide range of guests, such as organics, inorganics, and biomolecules. The aforementioned features lead to an extensive range of applications of β-CD, as the properties of β-CD mean that it is environmentally friendly and can be recovered and reused without mass loss. Here, the β-CD-catalyzed anti-Markovnikov addition of styrene to thiophenol in the presence of aerial oxygen and in aqueous solution to give 1-phenyl-2-(phenylsulfanyl)-1-ethanol was studied using density functional theory (DFT) and the Hartree-Fock (HF) method. The optimal configuration of the inclusion complex of styrene and thiophenol within β-CD was obtained, which indicated that styrene and thiophenol enter from the secondary and primary hydroxyl ends of β-CD, respectively. Moreover, hydrogen bonding of β-CD with styrene and thiophenol contributes to the stability of the inclusion complex. An investigation of the charges from electrostatic potentials using a grid-based method (CHELPG) highlighted the distribution of atomic charges upon complexation. The reaction sites of styrene and thiophenol were determined based on electrostatic potentials (ESPs) and condensed dual descriptors. The calculated 1H nuclear magnetic resonance (1H NMR) spectrum of β-CD implied that the chemical shifts of its protons change and H3 and H5 move to higher fields upon complexation, while the calculated 13C nuclear magnetic resonance (13C NMR) spectrum of styrene suggested that this molecule is electrophilic. Graphical abstract ᅟ.