Unrevealing the Nitrogen Elusive Chirality of 3‐Sulfanyl and 3‐Sulfinyl N‐Tosyl Isoindolinones by ECD Spectra: An Experimental and Theoretical Investigation

Abstract

The nitrogen‐hybridization/pyramidalization of two solvated N‐tosylisoindolinone derivatives having chiral residues in adjacent (I) or adjacent and distal (II) position has been investigated by a theoretical‐computational procedure based on Molecular Dynamics simulations and Quantum‐Chemical calculations. After validation of our strategy in providing a reliable repertory of conformations through the modeling of the electronic circular dichroism (EDC) spectra, the electronic features associated with N‐pyramidalization were further characterized by Natural Bond Order (NBO) analysis. Using the N‐geometry found in crystal structures as a reference, our findings reveal that the presence of neighbouring chiral centers generates sharper N‐pyramidalization in solution than in the solid state, both in I and II. Furthermore, although NBO analysis confirms that the N‐lactam mostly retains the sp2 character, its slight configurational distortion (ξI = 13°; ξII = 21°) emerges significantly in the chiroptical activities exhibited by I and II in ECD spectra, thereby substantiating these N‐lactams as configurationally stable chiral centers.