Molecular Rearrangement of 9b-Hydroxy-1H-imidazo[4,5-c]quinoline-2,4-diones - A Convenient Pathway to Spiro-Linked Imidazolidine-Oxindole Derivatives

The 1-substituted 3-alkyl/aryl-3-aminoquinoine-2,4(1H,3H)-diones 1 react with alkyl/aryl isocynates to give 3-alkyl/aryl-3-ureidoquinoline-2,4(1H,3H)-diones (=N-(3-alkyl/aryl-1,2,3,4-tetrahydro-2,4-dioxoquinolin-3-yl)ureas) 2 and/or 3a-alkyl/aryl-3,3a,5,9b-tetrahydro-9b-hydroxy-1H-imidazo[4,5-c]quinoline-2,4-diones 3 in high yields. Compounds 2 and 3 rearrange by boiling in AcOH or concentrated HCl solution to give three different types of spiro[imidazolidine-4,3'[3H]indole]-2,2'(1'H)-diones, i.e., 10, 11, and 12, depending on the kind of substituents at C(3) and C(3a), respectively. All compounds were characterized by (1)H- and (13)C-NMR and IR spectroscopy as well as by atmospheric-pressure chemical-ionization (APCI) mass spectra. The structures of compounds 11c and 12Al were investigated by single-crystal X-ray diffraction analysis.