2,2'-Dihydroxybenzil: a stereodynamic probe for primary amines controlled by steric strain

Area of Science:

• Organic Chemistry
• Stereochemistry
• Chiral Analysis

Background:

• Axial chirality is crucial in asymmetric synthesis and molecular recognition.
• Developing efficient methods for generating and determining axial chirality remains a significant challenge.
• Small organic receptors offer potential for creating well-defined chiral environments.

Purpose of the Study:

• To present a rational strategy for inducing 1,1'-binaphthalene-like axial chirality in a small organic receptor.
• To investigate the stereoselective formation of diimines from 2,2 dihydroxybenzil and primary amines.
• To establish a method for determining the absolute chirality and enantiomeric excess of primary amines using spectroscopic techniques.

Main Methods:

• Synthesis of the 2,2 dihydroxybenzil receptor.
• Reaction of the receptor with primary amines to form diimine derivatives.
• Analysis of stereoselectivity using experimental data.
• Computational simulation of circular dichroism (CD) spectra using time-dependent density-functional theory (TD-DFT).

Main Results:

• The 2,2 dihydroxybenzil receptor successfully formed diimines with primary amines.
• Axial chirality was induced with moderate to good stereoselectivity (1.4:1 to 4.7:1), controlled by steric strain.
• TD-DFT computations accurately simulated the observed CD spectra.
• The simulated CD spectra correlated with the absolute chirality and enantiomeric excess of the primary amines.

Conclusions:

• A novel and rational approach for generating axial chirality in organic receptors has been demonstrated.
• The diimine formation provides a robust system for controlling stereoselectivity in primary amine derivatives.
• CD spectroscopy, supported by TD-DFT calculations, serves as a reliable tool for chiral analysis of primary amines.