Sankyo Company, Limited

Teiji Omino

Teruomi Jojima

Hideakira Tsuji

Shinjiro Yamamoto

New organic phosphorus compounds having the formula ##STR1## wherein R.sub.1 represents an alkyl group of 1-4 carbon atoms, R.sub.2 represents an alkoxy group of 1-4 carbon atoms or phenyl group and R.sub.3 represents hydrogen atom, an alkyl group of 1-4 carbon atoms, phenyl group or the group of the formula -X-R.sub.4 in which R.sub.4 represents an alkyl group of 1-6 carbon atoms or a benzyl group which may be substituted with a halogen atom in the phenyl moiety and X represents oxygen atom or sulfur atom. The present compounds are prepared by reacting a phosphoric or phosphonic acid halide having the formula ##STR2## wherein R.sub.1 and R.sub.2 are as defined above and Y represents a halogen atom with a pyridazinone derivative having the formula ##STR3## wherein R.sub.3 is as defined above. The present compounds show a superior insecticidal activity against various harmful insects, e.g., rice stem borers, planthoppers, mites, aphids, flies, mosquitoes and the like and thus they are useful as an insecticide or acaricide.

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Shiga, Japan

Teiji Omino