Plausible Pnicogen Bonding of epi-Cinchonidine as a Chiral Scaffold in Catalysis

Abstract

As a non-covalent interaction of a chiral scaffold in catalysis, pnicogen bonding of epi-cinchonidine (epi-CD), a cinchona alkaloid, was simulated to consider whether the interaction can have the potential controlling enantiotopic face like hydrogen bonding. Among five reactive functional groups in epi-CD, two stable complexes of the hydroxyl group (X-epi-CD1) at C17 and of the quinoline ring (X-epi-CD2) at N16 with pnictide family analytes [X = substituted phosphine (PX), i.e., F, Br, Cl, CF3, CN, HO, NO2, and CH3, and pnictide family analytes, i.e., PBr3, BiI3, SbI3, and AsI3] were predicted with intermolecular interaction energies, charge transfer (QMulliken and QNBO), and band gap energies of HOMO–LUMO (Eg) at the B3LYP/6-31G(d,p) level of density functional theory. It was found that the dominant site of pnicogen bonding in epi-CD is the quinoline ring (N16 atom) rather than the hydroxyl group (O36 atom). In addition, the UV-Vis spectra of the complex were calculated by time-dependent density functional theory (TD-DFT) at the B3LYP/6-31+G(d,p) level and compared with experimental measurements. Through these calculations, two intermolecular interactions (H-bond vs. pnicogen bond) of epi-CD were compared.

Involvement of Arsenic Atom of AsF3 in Five Pnicogen Bonds: Differences between X-ray Structure and Theoretical Models

“…They can reverse the energetic balance between the chair and twist-boat conformations of cyclohexane [ 26 ]. The PnB is often involved in catalysis [ 27 , 28 ]: some examples include a chiral scaffold [ 29 ], enantioselective transfer hydrogenation of benzoxazines [ 30 ], and polyether cascade cyclizations [ 31 ]. Applications have been studied in terms of halide binding [ 32 , 33 , 34 , 35 ] and as a common factor in biological contexts [ 36 , 37 ] such as proteins and nucleic acids [ 38 ].…”