An Investigation Of Atropisomerism In Ortho-Imide Substituted 1,3-Benzoxazine By Experimental Nmr And Dft Calculations

A new type of atropisomerism in ortho-imide functional 1,3-benzoxazine compound was evident from nuclear magnetic resonance (NMR) spectra, which showed constant branching ratio of the two products at different measurement temperatures of NMR. Density functional theory calculations were performed to obtain molecular-level insights into the atropisomerism, which suggested that the reaction intermediate, ortho-imide phenol, determines the branching ratio of the products. Our calculations showed a large energy barrier after deprotonation of this molecule, which prevents any configurational switch in the follow-on reactions. Potentially, the atropisomerization mechanism discovered in this work can be used as a generic design principle for improving drug development, organic catalysts, molecular electronics, and other fields wherever atropisomers can play important and prevalent roles.