The reaction of 4-chloro-1, 8-naphthalic anhydride with sulfur and sodium sulfide in boiling ethanol lead to 4-mercapto-1, 8-naphthalic anhydride. The condensation of a later compound with amines produced 4-mercapto-1, 8-naphthalimides and with ethylenediamine and orthophenylenediamine, respectively, led to 4-mercapto-7H-imidazo [2, 1-a] benz [d, e] isoquinoline-7-one and 4-mercapto-7H-imidazo [2, 1a] benz [d, e] ...