New cascade transformations of 3-(2-aminophenyl- amino)-5,5-dimethyl-2-cyclohexen-1-one

The reaction of 3-(2-aminophenylamino)-5,5-dimethyl-2-cyclohexen-1-one with alloxan results in 3,3-dimethyl-1,2,3,4,10,11-hexa- hydrospiro(1 H -dibenzo[ b , e ][1,4]diazepine)-11,5 ’ -pyrimidine-1,2 ’ ,4 ’ ,6 ’ -tetraone or N -aminocarbonyl-1-(2-aminophenyl)-3-hydroxy- 6,6-dimethyl-2,4-dioxo-2,3,4,5,6,7-hexahydro-1 H -indole-3-carboxamide. The latter undergoes isomerization on dissolution in DMSO or DMF to give 5-[2-(2-aminophenylamino)-4,4-dimethyl-6-oxocyclohexenyl]-5-hydroxypyrimidine-2,4,6(1 H ,3 H ,6 H )-trione, thus demonstrating a new example of ring–ring tautomerism.