Oxydehydrogenative aromatization of fused 3-aminopyran-2-ones on carbon surfaces: a simple approach towards 3-amino-5-hydroxycoumarin derivatives

摘要

Aromatization of selected 3-acylamino-5,6,7,8-tetrahydro-2H-1-benzopyran-2,5-diones, yielding the corresponding 3-acylamino-5-hydroxycoumarins, was achieved by dehydrogenation with molecular oxygen in the presence of activated carbon. The use of nonpolar solvents and high temperatures was crucial for attaining satisfactory conversions. The 3-benzoylamino-5,6,7,8-tetrahydrocoumarin without a 5-keto group and the 8-oxo analogue as well as the 5-oxo-5,6,7,8-tetrahydrocoumarins containing a free 3-amino group were less efficiently aromatized.