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Novel π 2s +π 2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis ‐Fused with a Cyclopentene
Author(s) -
Dillenschneider JeanMarc,
Dufossé Laurent,
Fouillaud Mireille,
Sutthiwong Nuthathai,
Labia Roger,
Valla Alain
Publication year - 2016
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.2419
Subject(s) - conrotatory and disrotatory , chemistry , cyclopentene , electrocyclic reaction , ring (chemistry) , intramolecular force , stereochemistry , medicinal chemistry , organic chemistry , catalysis
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 π 2s + π 2a conrotatory process. This cyclopentenyl cation led to unstable γ‐lactones intermediates that are rearrange to more stable isomers. δ‐lactones (6 Z and 6 E ‐(3‐chlorobut‐2‐en‐2‐yl)‐5‐methyl‐3,6‐dihydro‐2 H ‐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.