Sulfuric acid and Amberlyst-H+ catalyzed condensation reactions of renewable keto acids with paraformaldehyde: synthesis of a new dispiro bis-lactone ring system 2,9,13-trioxadispiro[4.1.4.3]tetradecane-3,6,10-trione

Abstract

The sulfuric acid and Amberlyst-H⁺ catalyzed condensation reactions of renewable feedstock levulinic acid with paraformaldehyde under neat conditions at 80 °C gives 2,9,11,14-tetraoxadispiro[4.1.5.3]pentadecane-3,6-dione in 91–93% yield, in which the structure was confirmed by single crystal X-ray crystallography. A similar condensation reaction between 4-ketopimelic acid and paraformaldehyde at 80 °C gives 2,9,13-trioxadispiro[4.1.4.3]tetradecane-3,6,10-trione. This new dispiro bis-lactone was found to composed of a 1.6 : 1 mixture of isomers with planes of symmetry bisecting the tetrahydro-2H-pyran-4-one rings through the carbonyl groups.