Two‐step Synthesis of New γ‐Lactones via Cyclization of 7‐Chloro‐2‐(methoxycarbonyl)‐4‐6‐dimethylocta‐(2E,4E,6E)‐trienoic acid

Abstract

A new rapid synthesis of γ-lactones, cis fused with a cyclopentenic ring by thermal cyclization of 7-chloro-2-(methoxycarbonyl)-4-6-dimethylocta-7-phenyl (or methyl) (2E,4E,6E)-trienoic acids was reported. The key step implicates an intramolecular cyclization to a cyclopentenyl cation, according to an electrocyclic π 2s + π 2a conrotatory process, published in a recent paper (from the corresponding diacids). We have investigated the thermal behavior of the corresponding half-esters since; if the cyclization obeys to the proposed mechanism, the diacids, half-esters must also cyclize in a similar manner. Saponification of these led to γ-dilactones via intermediary cyclopropanes. Mechanistic pathways were investigated.

Recent Advances in the Interrupted Nazarov Reaction

“…Apart from 2,4‐dienocarbonyl compounds, 2,4,6‐trienes containing a dicarboxyl group at the terminal carbon atom are involved in the interrupted iso ‐Nazarov reaction (Scheme ) . The reaction proceeds under catalyst‐free conditions because it is promoted by a carboxyl group.…”