Claims
- 1. A compound of the formula ##STR7## in which one R and R.sup.1 is s-butyl and the other R and R.sup.1 is s-butyl or t-butyl.
- 2. The compound of claim 1 in which R is s-butyl, and R.sup.1 is s-butyl.
- 3. The compound of claim 1 in which R is t-butyl and R.sup.1 is s-butyl.
- 4. A method for controlling soil-borne insects and nematodes which comprises applying to the soil in which agricultural crops are planted or are to be planted a soil-borne insect and nematode controlling amount of the compound of claim 1, 2, or 3.
- 5. An insecticidal and nematicidal composition for residual control of soil-borne insects and nematodes comprising a soil-borne insect and nematode controlling amount of the compound of claim 1, 2, or 3 in admixture with at least one agriculturally acceptable diluent, carrier, or adjuvant.
Parent Case Info
This application is a divisional of U.S. patent application Ser. No. 470,736 filed Feb. 28, 1983, which is a continuation-in-part of U.S. application Ser. No. 297,437 filed Aug. 28, 1981, both now abandoned.
The present invention relates to pesticidal compounds which are O-ethyl S,S-dialkyl phosphorodithioates in which one or both of the S-alkyl groups is an s-butyl group and the other is an s-butyl group or t-butyl group. The compounds of this invention exhibit uniquely high levels of control of both soil borne insects and nematodes, low phytotoxicity, and excellent residual activity when incorporated into the soil in which agricultural crops are or are about to be planted.
Agricultural chemicals normally used in the control of soil insects and nematodes suffer the disadvantages that they are either (1) highly active against soil insects but low in nematicidal action or (2) highly nematicidal but much less active against soil insects.
Also, agricultural practices necessitate application of soil pesticides as a single application at the beginning of the planting season to protect the roots of the plants from insects and nematodes throughout the growing period. In particular the root damaging stages of insects, for example corn rootworm larvae, will appear several weeks after planting time. Therefore it is important that soil chemicals exhibit long residual action and be of low phytotoxicity during the growing period of plants. For this reason soil pesticides having short residual activity are undesirable.
These disadvantages have resulted in the application of two chemicals, one as an insecticide and the other as a nematicide, or the use of high application rates of one chemical to overcome poor insecticidal activity, poor nematicidal activity, or short residual activity of that chemical.
U.S. Pat. No. 3,112,244 discloses compounds of the formula: ##STR2## in which X is oxygen or sulfur and each R is a lower alkyl group, but does not disclose compounds in which R.sup.1 is .alpha.-branched. The compounds of this patent are used for control of nematodes, but have low residual soil insect and nematicidal activity.
Japanese Patent Publication No. 29847/1969, published Dec. 3, 1969, relates to a process for preparing certain dithiophosphate esters said to have strong fungicidal, insecticidal, acaricidal, and nematicidal activities. This publication discloses, inter alia, compounds of the general formula ##STR3## In one specific embodiment R is ethyl and A and B are each t-butyl. In another R is ethyl, one of A and B is s-butyl, the other of A and B is n-butyl. While each of these compounds is highly active against nematodes or against soil borne insects, neither is highly active against both groups of crop pests.
The present invention provides compounds having the desired combination of properties, namely long soil residual insecticidal activity, high nematicidal activity, and low phytotoxicity. The compounds having these properties are O-ethyl S,S-dialkyl phosphorodithioates having the formula: ##STR4## in which one of R and R.sup.1 is s-butyl and the other of R and R.sup.1 is s-butyl or t-butyl.
These compounds are highly active against both pest groups at extremely low application rates. They also exhibit unexpectedly high residual activity against soil borne insects. Both compounds of this invention also exhibit high residual activity against nematodes at low application rates, and are without any substantial phytotoxic effect at normal use levels. The combination of all these desirable features in a single compound is highly unexpected.
The compounds of this invention may be prepared by reacting S-alkyl phosphorothioic dichloride (II) with ethanol to produce an O-ethyl S-alkyl phosphorothioic chloride (III) in accordance with the general reaction: ##STR5## then reacting III with a basic salt, for example an alkali metal or alkaline earth metal salt, of an alkanethiol to produce the compound of this invention, in accordance with the general reaction ##STR6##
The foregoing sequence of reactions is particularly desirable to maximize yields when R is a tertiary alkyl group.
The compounds of this invention in which R and R.sup.1 are the same may suitably be prepared in like manner or by reacting 2 molar equivalents of an alkanethiol salt with one molar equivalent of an O-ethyl phosphoric dichloride.
Another method for preparing the compounds of this invention is by reacting an alkanesulfenyl chloride with a diethyl chlorophosphite to produce III (K. A. Petrov et al., Zh. Obsheh. Khim. 26, 3381-4 1956), then reacting that with an alkanethiol salt as shown above.
US Referenced Citations (6)
Foreign Referenced Citations (3)
| Number |
Date |
Country |
| 29847 |
Dec 1969 |
JPX |
| WO8300870 |
Mar 1983 |
WOX |
| 1081270 |
Aug 1967 |
GBX |
Divisions (1)
|
Number |
Date |
Country |
| Parent |
470736 |
Feb 1983 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
297437 |
Aug 1981 |
|
Patent Grant
4535077
