[Figure not available: see fulltext.] The treatment of 5-[2-(dimethylamino)benzylidene]-3-methyl-2-(methylsulfanyl)-3,5-dihydro-4H-imidazol-4-ones with catalytic amounts of scandium triflate resulted in a [1,5]-hydride shift followed by cyclization, giving 1,1'-dimethyl-2-(methylsulfanyl)-1',4'-dihydro-2'Hspiro[imidazole-4,3'-quinolin]-5(1H)-ones. All of the newly synthesized compounds containing various substituents in the benzylidene moiety were isolated in good yields.