Structure of the Cycloaddition Products of Pyrido[2,1-a]isoindole with Maleimide Derivatives: X-ray Diffraction Analysis and1H NMR Variable-Temperature Spectra

Abstract

Investigation of the cycloaddition reaction under thermodynamic control of pyrido[2,1-a]isoindole with maleimide derivatives revealed a new rearrangement leading to 2-{2′-[(1R)2,5-dioxopyrrolidinylidene]-2′-[(1R)-2,5-dioxopyrrolidinyl)methyl]}phenylpyridine. Their structure was confirmed by X-ray diffraction analysis. The atropisomeric properties of the obtained compounds were examined in a detailed NMR spectroscopic study. Dependence of the spectra on temperature was investigated, and coalescence temperatures and conversion barriers between the corresponding atropisomers determined.