Ciba-geigy Corporation

Gottfried Bohtz

Gunter Mattern

Erik Frandsen

Novel 3-phenyl-2-thioxo-2H,5H-pyrano[3,2-c][I]benzopyran-5-one derivatives, a process for their manufacture, compositions which contain these compounds as active substances for controlling harmful rodents, and the use of the active substances, or of compositions which contain them, as rodenticides. The novel 3-phenyl-2-thioxo-2H,5H-pyrano[3,2-c][I]benzopyran-5-one derivatives have the general formula I ##STR1## wherein each of R and R' independently represents hydrogen, alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, or halogen.

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Basel, Switzerland

Gottfried Bohtz