Cyclohexanone, 4-methylcyclohexanone, and phloroglucinol, when treated with carbondisulfide in the presence of triethylamine and aqueous ammonia, gave the respective 3,1-benzothiazine-2(1H),4-dithiones. Glutazines and 2-iminocyclopentanedithiocarboxylic acid underwent this reaction without ammonia.