Enantiomers and barriers to racemization of sterically hindered N-aryl- and N-heteroarylpyrroles |
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Authors: | Jasna Vorkapi-Fura
Mladen Mintas Fritz Kastner Albrecht Mannschreck |
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Institution: | Jasna Vorkapić-Furač,Mladen Mintas,Fritz Kastner,Albrecht Mannschreck |
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Abstract: | The N-aryl- and N-heteroaryl-2,5-dimethylpyrrole-3-carbaldehydes 2–8 have been synthesized by condensation of hexane-2,5-dione with the appropriate amine and subsequent Vilsmeier-Haack formylation of the pyrrole ring. Diastereomeric association complexes of the racemic pyrrole 8 were studied by pmr chemical shifts and the splittings induced by (+)-1-(9-anthryl)-2,2,2-trifluoroethanol. Enrichment of the enantiomers M and P of 2 and 6 was achieved by liquid chromatography on triacethylcellulose. The barrier to partial rotation about the C-N bond in 6 was determined by thermal racemization and its lower limits in 2 and 8 were estimated. |
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