Novel π2s+π2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene |
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| Authors: | Jean‐Marc Dillenschneider Laurent Dufossé Mireille Fouillaud Nuthathai Sutthiwong Roger Labia Alain Valla |
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| Affiliation: | 1. Laboratoire de Chimie des Substances Naturelles, URA 401 CNRS, MNHN, Paris, France;2. Université de La Réunion, ESIROI Département Agroalimentaire, Laboratoire de Chimie des Substances Naturelles et des Sciences des Aliments, Sainte‐Clotilde, La Réunion, France;3. Thailand Institute of Scientific and Technological Research, Agricultural Technology Department, Pathum Thani, Thailand;4. Chimie et Biologie des Substances Naturelles FRE 2125 CNRS, MNHN, UBO, Quimper, France |
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| Abstract: | A new, easy and rapid synthesis of γ‐dilactones is cis‐fused with a cyclopentenic ring via cyclization of 7‐chlorotriethylenic‐malonic acids. The key step implicates an intramolecular cyclization to a cyclopentenyl cation, according to an electrocyclic π2s + π2a conrotatory process. This cyclopentenyl cation led to unstable γ‐lactones intermediates that are rearrange to more stable isomers. δ‐lactones (6Z and 6E‐(3‐chlorobut‐2‐en‐2‐yl)‐5‐methyl‐3,6‐dihydro‐2H‐pyran‐2‐one) were obtained as secondary products. Mechanistic pathways were considered. The structures of the newly synthesized compounds were established by elemental and spectral data. |
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