Suggested Reaction 1.3.3.-

Left

5,6-Dihydroxy-3-methyl-2-oxo-1,2,5,6-tetrahydroquinoline
+O2

Right

5,6-Dihydroxy-3-methyl-2-oxo-1,2-dihydroquinoline
+H2O2

[BiSSCat | GREP ]