Nucleophile-Dependent Substitution Reactions of 5-Halovaleric Acid Esters: Synthesis of 6,12-Dioxamyristic Acid

The reaction of 5-ethoxypentan-1-ol with a variety of 5-halovalerate alkyl esters afforded ester exchange products rather than the expected products of Williamson ether synthesis. The virtually unknown reaction of an alkoxide with a 5-halovalerate ester contrasts strongly with literature reports of reactions involving other nucleophiles in which the halogen substitution products are nearly always isolated. An explanation is offered for this behavior in terms of a chelation-induced conformation of the substrate. Although the direct synthetic approach failed, the hitherto unknown title compound could still be prepared, albeit in six steps in 6% overall yield. The approach used is discussed along with the interesting chemistry of this system.