“…Isatin and oxindole condense in acid media (50,71,122,138,156,200,201,203,204,205,206) to give isoindigo (I) and in the presence of pyridine to give isatane (II) (71,128,132,138,156,204,206). Oxindole and nuclear-substituted oxindoles condense with nitrosobenzene (156) and with p-nitrosodimethylaniline (156,180) to give derivatives of isatin-…”