Study of H-bonds of two pseudo-resonance aggregation state structures using variable-temperature NMR

In chiral pseudo-resonance alcohols, two conformers A and B possess different sizes since their corresponding bond lengths and angles are different. Both conformers A and B co-exist together in general via an intermolecular H -bonds. (S)-3-((1R,3R)-3-hydroxy-1,3-dihydroisobenzofuran-1-yl)-2-isopropylisoindolin-1-one (lactone) and natural alcohol talaromytin were investigated to study the stability of H -bonds using variable-temperature 1H NMR spectra. The experimental results show that the H -bonds between two conformers A and B of the lactone could remain in DMSO-d6 at 353 K while the H -bonds in talaromytin were broken near 343 K in DMSO-d6. The alternative bond length changes were partially recorded using quantum theory at the B3LYP/6-311+G(d) level for two conformers A and B of the lactone.