Prepn by dimerization reduction of isatin with ammonium hydrosulfide: Laurent, Ann. Chim. 3, 372 (1841); by piperidine-catalyzed condensation of isatin and dioxindole: Heller, Ber. 37, 943 (1904); Wahl, Hansen, Compt. Rend. 178, 393 (1924); from isatin and acenaphthene in sunlight: Oliveri-Mandala, Deleo, Gazz. Chim. Ital. 79, 337 (1949). Structure: Lefèvre, Bull. Soc. Chim. Fr. 19, 113 (1916); Sumpter, J. Am. Chem. Soc. 54, 2917 (1932); Bergmann, ibid. 77, 1549 (1955).
This monograph has been retired and is no longer subject to revision or update.