Abstract γ-Carboxylation of β-diketones, 1, can be improved using samples containing 100% of ketoenol tautomers, 3, prepared by mild hydrolysis of the corresponding copper (II) complexes 2. Cyclization of the so formed 4-alkyl-3, 5-dioxohexanoic acids, 4, affords 5-alkyl- 4-hydroxy-6-methyl-2-pyrones, 5.
