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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Submitted on : Saturday, November 19, 2016 - 8:39:09 AM
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Jean-Marc Dillenschneider, Laurent Dufossé, Mireille Fouillaud, Nuthathai Sutthiwong, Roger Labia, et al.. Novel π2s+π2a Electrocyclization of Triethylenic-Malonic Acids Exemplified for a One-Pot Synthesis of New γ-Dilactones cis-Fused with a Cyclopentene. Journal of Heterocyclic Chemistry, Wiley, 2016, 53 (4), pp.1017-1021. ⟨http://onlinelibrary.wiley.com/doi/10.1002/jhet.2419/abstract⟩. ⟨10.1002/jhet.2419⟩. ⟨hal-01188092⟩
