Diarylamines with the Neighboring Pyridyl Group: Synthesis and Modulation of the Amine Functionality via Intramolecular H-Bonding

Abstract

New pyridyl-containing diarylamines were obtained via Cu-assisted reductive amination of the ortho-2-pyridylarylboronic acids. Comparative analysis of the spectral and electrochemical data obtained for new diarylamines and their pyridyl-free counterparts revealed the intramolecular H-bond (IMHB) formation which significantly influences the properties of the amino group. The electron density at the N atom of the amino group is increased due to partial weakening of the N–H bond, although the BDE and activation energy for the H-atom abstraction is increased due to the chelating effect of two N atoms. The ortho-pyridyl-containing diarylamines are more prone to be oxidized as compared to their pyridyl-free counterparts; the shift in the oxidation potential values correlates with the strength of the intramolecular H-bonding which can be tuned by inserting substituents in the pyridyl or phenyl rings. The IMHB is reserved even in polar solvents having a significant H-acceptor ability (such as DMSO) but can be destroyed in methanol, testifying in favor of the dynamic nature of the H-bonding.

N,N′-Diaryldihydrophenazines as Visible-Light Photocatalysts for Anilines’ Arylation Using a Dual Photoredox/Ni(II) Cross-Coupling Strategy

“…All reagents were obtained from commercial sources and used without purification unless otherwise stated. Amine 2k was synthesized as described previously …”

“…Amine 2k was synthesized as described previously. 40 para-tert-Butylaniline, para-methoxyaniline, and para-fluoroaniline were distilled under vacuum prior to use. The photoredox catalysts (Phz1 and Phz2) were synthesized as previously reported.…”