Structure Confirmation of Quinazolinone and Hydroindole Using Residual Dipolar Couplings From Polyarylisocyanide Liquid Crystal

Determining the constitution and configuration is a critical step in characterizing the structure of small molecules. In addition to the classical nuclear magnetic resonance (NMR) method conducted in isotropic solutions, the emerging anisotropic NMR parameters such as residual dipolar couplings (RDCs) were also employed to clarify the structures of organic molecules. These RDCs not only confirmed that the unexpectedly synthesized product was a quinazolinone but also validated the relative configuration of the diastereoisomeric hydroindole in a polyarylisocyanide lyotropic liquid crystalline solution through the induction of anisotropy. Singular value decomposition (SVD) was employed to fit the experimental RDC data against the low-energy conformational sets of an unexpected synthetic product, which were calculated using density functional theory (DFT). This analysis aimed to identify the correct molecular connection sites. Furthermore, the method was applied to determine the correct relative configuration between two possible diastereoisomers.