Generation of functionalized azomethine ylides and their application to stereoselective heterocycle synthesis: an equivalent process of C-unsubstituted nitrile ylide cycloaddition reaction |
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Authors: | Keisuke Kawashima Michihiko Noguchi |
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Institution: | a Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University, Tokiwadai, Ube 755-8611, Japan b Department of Chemistry and Material Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan |
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Abstract: | The synthetic process equivalent to C-unsubstituted (CH) nitrile ylides cycloaddition reaction is achieved via cycloaddition of NH-azomethine ylide and the following fission reaction of the cycloadducts under acidic conditions. Cycloaddition of NH-azomethine ylide generated by a thermal 1,2-prototropy in 4-oxo-4H-pyrido1,2-a]pyrimidine-3-carbaldehyde system with maleimides provides proline derivatives under extremely mild conditions. Heating their adducts in AcOH at 85 °C causes a cleavage of C-C bond between the proline and heterocyclic moiety to give the parent heterocyclic system and dehydroproline derivatives, which is regarded as a cycloadduct of C-unsubstituted (CH) nitrile ylide. This cycloaddition-fission reaction sequences can be applied to one-pot three-component reaction. |
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