Syntheses, and Structural and Physical Properties of Axially Chiral Biaryl Dicarboxylic Acids Bearing Chalcogen Atoms

Abstract

The preparation, optical resolution, and structural investigations of a series of axially chiral biaryl dicarboxylic acids bearing oxygen, sulfur, and selenium atoms were carried out. The crystal structures of sulfur-and selenium-containing derivatives revealed that the carboxy groups of these compounds are located in a co-planar geometry with the fused aromatic rings including the chalcogen atoms. These conformational controls were found to be achieved by chalcogen-bonding interactions between chalcogen atoms in the aromatic rings and oxygen atoms in the carboxy groups. Even in the case of a binaphthofuran derivative, in which the formation of chalcogen-bonding interactions was expected to be negligible, the carboxy groups were also found to be located in a co-planar geometry toward its fused cyclic rings. Natural bond orbital (NBO) analyses of these dicarboxylic acids indicated the formation not only for the chalcogen-bonding interactions for S and Se derivatives, but also the tetrel-bonding interactions between the oxygen atoms in the carboxy groups and the carbon atoms in the fused cyclic rings for all biaryl dicarboxylic acids. These tetrel-bonding interactions were thought to contribute to conformational control in the binaphthofuran derivative. Physical and chiroptical properties such as the racemization barriers and circular dichroism (CD) spectra of these biaryl dicarboxylic acids were also revealed.

Dual Chalcogen-bonding interactions for the conformational control of urea

“…In the NMR spectra, a progressive downfield shift of the carbonyl carbon signal in the 13 C NMR spectrum was observed for 5 (148.8 ppm), 1a (151.0 ppm), and 1c (151.4 ppm) in DMSO-d6 (Table 1). 20,21 These downfield shifts are consistent with the strength of the chalcogen-bonding interaction, therefore confirming the presence of these chalcogen bonds even in solution. Moreover, the 1 H NMR signals of the N-H groups in DMSO-d6 were also shifted downfield from 9.92 ppm (5) to 10.19 ppm (1a), and 10.43 ppm (1c), which is in agreement with the strength of their chalcogen-bonding interactions.…”