Investigations of Two-Set of NMR Spectra of 3-Substituted Isoindolin-1-ones

Two amines, (4-chlorophenyl)methanamine and 2-(4-chlorophenyl)ethan-1-amine were used for syntheses of two substituted isoindolin-1-ones (4 and 5), in which the framework isoindolin-1-one exhibited some bioactivities. In this report, two sets of NMR signals were recorded for the both 4 and 5, which are different from the traditional framework. Variable-temperature (VT) 1H NMR exhibited that the two sets of NMR signals did not coalesce into one set in high temperatures. Potential energy surface (PES) scan was performed at the omega B97XD/ 6-31+G(d) level. The effects of the sample's concentrations and four deuterated solvents on the NMR spectra were investigated. Finally, the compound 5 was transferred to the corresponding methyl ether 6, which just had one set of NMR spectra. All results exhibit that formation of H-bond between two structures (4 or 5) plays the key role to produce the two sets of NMR data.