Recent Advances in the Application of Vibrational Circular Dichroism Spectroscopy for the Characterization of Asymmetric Catalysts

In this Minireview, we summarize our recent efforts to use vibrational circular dichroism (VCD) spectroscopy, the chiroptical version of IR spectroscopy, for the characterization of conformational preferences of asymmetric catalysts and complexes, formed upon the respective interactions or reactions of catalysts with substrates. After giving a brief overview of the general aspects of the technique, we showcase how VCD spectra of a chiral ion-pairing catalyst could be used to confirm a conformational shifting mechanism that determines the enantioselectivity of the catalyst. Chiral thioureas serve as examples for hydrogen bonding organocatalysts for which we demonstrate that both conformational preferences of the catalysts as well as of the hydrogen-bonded complexes with substrates can be obtained from a detailed computational spectra analysis. Jorgensen-Hayashi-type prolinol ether catalysts serve as examples to introduce experimental challenges associated with catalysts that operate by covalent activation of reactants.