Unusual formation and helicity induction in a para-amino-substituted trityl chromophore: a cautionary note

O- and N-trityl derivatives Ph3C∗-X-R∗ of chiral alcohols (X=O) and amines (X=NH) are known to produce strong and stereochemically predictable Cotton effects in the Electronic Circular Dichroism (ECD) spectra due to the preferred M or P helical conformation of the trityl group. With the use of ECD spectra in solution and crystal X-ray diffraction analysis, we demonstrate that in a chiral p-substituted trityl derivative p-R∗N(Me)-C6H4-C∗Ph2H, the stereochemical information is transmitted from a permanent stereogenic center R∗ to the dynamic C∗ stereogenic center of the trityl sensor via the para carbon atom, and not through the central carbon atom.