Structure of the cycloaddition products of pyrido[2,1-a]isoindole with maleimide derivatives: X-ray diffraction analysis and H-1 NMR variable-temperature spectra

Investigation of the cycloaddition reaction under thermodynamic control of pyrido[2,1-a]isoindole with maleimide derivatives revealed a new rearrangem ent leading to 2-{2 '-[(1R)2,5-dioxopyrrolidinylidene]-2 '-[(1R)-2,5-dioxop yrrolidinyl)-methyl]}phenylpyridine. Their structure was confirmed by Xray diffraction analysis. The atropisomeric properties of the obtained compound s were examined in a detailed NMR spectroscopic study. Dependence of the sp ectra on temperature was investigated, and coalescence temperatures and con version barriers between the corresponding atropisomers determined.