Reaction of 1-substituted 3-aminoquinoline-2,4-diones with isothiocyanates. An easy pathway to generate novel 2-thioxo-1′H-spiro[imidazoline-5,3′-indole]-2,2′-diones

3-Butyl-3-amino-1H,3H-quinoline-2,4-diones react with isothiocyanates to give novel 3a-butyl-9b-hydroxy-2-thioxo-1,2,3,3a,5,9b-hexahydro-imidazo[4,5-c]quinolin-2-ones in high yields. These compounds rearrange in boiling acetic acid or concd hydrochloric acid to give (E)- and/or (Z)-4-butylidene-2-thioxo-1′H-spiro[imidazoline-5,3′-indole]-2,2′-diones. All compounds were characterized by their 1H, 13C, IR and MS spectra, and some of them also by 15N NMR. The structure of one compound was investigated by single-crystal X-ray diffraction.