Reaction of 1-substituted 3-aminoquinolinediones with isocyanic and isothiocyanic acid

1-Substituted-3-aminoquinoline-2,4(1H,3H)-diones react with potassium cyanate or potassium thiocyanate in boiling acetic acid to give ureido- or thioureidooxindoles, spiro-oxindoles and dihydroimidazoquinolones. However, if the starting compounds are substituted with a benzyl group at position 3, a C-debenzylation proceeds to give imidazoquinolones. According to a proposed reaction mechanism, a molecular rearrangement of the primarily formed mono-substituted urea or thiourea takes place. All compounds were characterized by 1H, 13C and IR spectroscopy and MS data.