The structure of glutaconic anhydride and the synthetic utility of its Diels–Alder adduct with cyclopentadiene

Abstract

In non-polar solvents glutaconic anhydride exists predominantly as its dioxo-tautomer (1). Diels–Alder reaction with cyclopentadiene affords 3-endo-carboxynorborn-5-en-2-endo-ylacetic acid anhydride (5) having considerable synthetic potential, and which on hydrolysis gives the corresponding bis-endo-dicarboxylic acid (6a). The dimethyl ester of (6a) may be epimerised and hydrolysed to the trans-dicarboxylic acid, 3-exo-carboxynorborn-5-en-2-endo-ylacetic acid (9a). The acids (6a) and (9a) have been characterised as a γ-iodolactone (7a) and a δ-iodolactone (13), respectively.