Amine salts of 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxides

Abstract: The compounds 1,4,2-oxazaphospholidine-4-­ acetic acid, 2-alkoxy-2-oxides and their trialkyl­ amine salts represented by the formula wherein R¹, R², R³ and R⁴ are individually selected from the group consisting of alkyl having from one to about four carbon atoms are useful as post emergent, selective herbicides and plant growth regulators.

Description: Background of the Invention This invention relates to novel organophosphorus amines, and more particularly relates to novel amine salts of 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxides and the use of such compounds as a herbicide and plant growth regulator. There are numerous references in the prior art that disclose various organophosphorus compounds. For example, U.S. Patent 3,172,903 discloses that certain 1,3,2-oxazaphospholidine and 1,3,2-oxazaphospholidine phosphorus ester compounds are useful as fungicides. U.S. Patent 4,190,651 discloses that certain 4-substituted 1,3,2-oxazaphospholidine derivatives are useful as insecticides. U.S. Patent 4,387,060 discloses a synergistic insecticidial composition containing 2-(thi)oxo-1,3,2-oxazaphospholane of defined formula. Other organophosphorus compounds are known to have biological activity on plants. For example, U.S. Patent 3,799,758 to Franz discloses that N-phosphonomethylglycine and its salts are useful as a broad spectrum herbicide and has a phytotoxic effect on most terrestrial and aquatic plants. U.S. Patent 4,486,359 to Brendel et al discloses that N-phosphonomethylglycine can be prepared from glycine and paraformaldehyde to obtain an intermediate which is reacted with a dialkylphosphite to obtain an ester of the desired compound, which is then hydrolized. U.S. Patent 4,062,669 to Franz disloses that N-organo-N-phosphonomethylglycine-N-oxides and derivatives thereof are useful in herbicidal compositions and methods, and that the compounds and the compositions containing them are useful as phytotoxicants and as plant growth regulants. U.S. Patent 4,601,744 to Sikorski et al discloses that esters of N,N′-methylene-bis-[N-[-(diaryloxyphosphinyl)methyl]glycine] are useful as herbicides. Despite these and other references in the prior art, there is now provided novel 1,4,2-oxazaphospholidine compounds that have selective phytotoxic activity, i.e. they have a herbicidal effect upon certain plant species but do not have a phytotoxic effect on other plant species, and have a plant growth regulant activity, i.e. stunt or retard the growth rate of certain plants without phytotoxicity. Summary of the Invention These and other advantages are achieved by compounds represented by the formula: wherein R⁴ is an alkyl group having from 1 to 4 carbon atoms. A particularly preferred embodiment of this invention is the tertiary amine salt of the 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxide represented by the above formula, and which amine salt can be represented by the following structural formula: wherein R¹, R² and R³ are individually selected from alkyl groups having from one to four carbon atoms. Detailed Description of the Invention Although applicants do not wish to be bound by any particular theory, it is believed that the 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxide compounds of the present invention, represented by the above formulas, enter the plant and form an anion as represented by the following structural formula: wherein R⁴ is as defined above. It is believed that this anion is responsible for the selective herbicidal activity and plant growth regulant properties exhibited by the novel compounds of the present invention. The compounds of the present invention can be prepared from the known reactants, glycine, formaldehyde, trialkylamine and dialkyl phosphite, i.e. dimethyl phosphite, diethyl phosphite, methylethylphosphite, diisopropylphosphite, dibutylphosphite and the like. Mixed esters and branched derivatives can also be used. Dimethylphosphite and diethylphosphite are preferred. Another reactant is a trialkyl amine wherein the alkyl group contains from one to about four carbon atoms. Examples of such trialkyl amines include trimethylamine, triethylamine, tributylamine, triisopropylamine, tri-t-butylamine, and mixtures such as diethylmethylamine, dibutylethylamine. Trimethylamine and triethylamine are preferred, since they are readily available. To prepare the compounds of the present invention, formaldehyde and a trialkylamine are heated to solution in an anhydrous solvent, such as methanol, ethanol, propanol, isopropanol, t-butanol, butanol. Methanol is preferred. Thereafter, glycine is added with heat and stirring, and then the dialkyl phosphite is added to the solution and heated. There is then provided the trialkylamine salt of 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxide. The acid can be prepared by passing the solution of the amine salt in anhydrous alcohol through a weakly acidic cation exchange resin to remove the trialkylamine and provide the 1,4,2-oxazaphospholidine-4-acetic acid, 2-alkoxy-2-oxides. The mole ratio of the reactants influences the yield of the desired product. In general, most of the reactants are in a mole ratio of about 1:1, based on glycine, except that formaldehyde should be used in excess, preferably 2:1 or 3:1 or higher. The temperature of the dialkyl phosphite addition can vary from about room temperature to about 75°C. Satisfactory results have been achieved at temperatures between about 25°C and about 60°C. The products of the above reaction are useful as selective post emergent herbicides by providing phytotoxic activity on cocklebur, morningglory, barnyardgrass, yellow nutsedge and quackgrass. The compounds are also useful to control the growth rate on desirable grasses, such as fescue. Typically the biologically active compounds of this invention are provided in the form of concentrates which require dilution prior to application to plants. The usual means for diluting the concentrate, whether either liquid or solid, comprising adjuvants, inert materials, are known to those skilled in the art. The compositions containing concentrates which require dilution prior to application to the plants contain from about 5 to 95 parts by weight of at least one compound of the present invention, and from 5 to 95 parts by weight of an adjuvant in liquid or solid form, for example, from about 0.25 to 25 parts by weight of a wetting agent, from about 0.25 to 25 parts by weight of a dispersant, and from about 4.5 to about 94.5 parts by weight of an inert liquid extender, such as water, acetone, tetrahydrofuran. The composition can also contain other materials as will occur to those skilled in the art in view of this disclosure. When operating in accordance with the teachings of the present invention, effective amounts of the compounds or compositions of the present invention are applied to the plants or are incorporated into aquatic media in any conventional fashion. The compositions can also be applied from airplanes as a dust or spray by means known to those skilled in the art. The application of an effective amount of the compound or composition of the present invention to the plant is essential and critical for the practice of the present invention. The exact amount of the active ingredient to be employed is dependent upon the response desired in the plant, as well as such other factors such as the plant species, stage of development, the amount of rainfall, as well as the specific compound employed. It is believed that one skilled in the art can readily determine from the teachings of this specification, including the examples, the approximate application rate. The invention is further illustrated by, but not limited to, the following examples, where all percentages are by weight unless otherwise indicated. Example 1 Preparation of triethylamine salt of 1,4,2- oxazaphospholidine-4-acetic acid, 2-methoxy-2-oxide . Triethylamine (5.05 g, 0.05 mol) and paraformaldehyde (3.0 g, 0.10 mol) were heated to solution (55°C) in methanol (50 ml). Glycine (3.75 g, 0.05 mol) was added in one portion and the mixture was heated at reflux for one hour. The solution was cooled to room temperature, and dimethyl phosphite (5.5 g, 0.05 mol) was added in one portion. The solution was heated at reflux for 40 minutes upon which time the ³¹P NMR spectra showed the absence of dimethyl phosphite. The methanol in the reaction mixture was removed on a rotary evaporator at 35°C and reduced pressure (25 mm, 33.35x10²N/m²) to yield 15.4 g of a light yellow oil, which was confirmed to be the desired compound by ¹H NMR, ¹³C NMR and ³¹P NMR spectral analyses. Example 2 Preparation of 1,4,2-oxazaphospholidine-4- acetic acid, 2-alkoxy-2-oxide . The procedure of Example 1 was repeated to obtain the light yellow oil, which was then dissolved in methanol (50 ml) and the solution was passed through a 30 cm long column of Amberlite™ CG-50 slightly acidic cation exchange resin available from Rohm & Haas Company of West Philadelphia, Pennsylvania. Analysis by ¹H NMR, ¹³C NMR and ³¹P NMR confirmed the presence of the desired compound. Example 3 Post-Emergent Herbicide Activity . The post-emergent herbicidal activity of the compound of Example 1 was demonstrated by greenhouse testing. Top soil was placed in pans having holes in the bottom and compacted to a depth of 0.95 to 1.27 cm from the top of the pan. A predetermined number of seeds of each of several plant species or vegetative propagules for perennial plant species were placed on the soil and pressed into the soil surface. The seeds or propagules were covered with soil and leveled. The pans were then placed on a bench in the greenhouse and watered as needed for germination and growth. After the plants reached the desired age (2 to 3 weeks) each pan, except the control pans, was removed to a spraying chamber and sprayed by means of an atomizer. In the spray solution, an emulsifying agent was added to give a spray solution which contains about 0.4% by volume of the emulsifier. The spray solution contained a sufficient amount of the compound of Example 1 to give an application rate of the active ingredient of 2.8 g/m² (25 lbs. per acre) and 5.6 g/m² (50 lbs. per acre), while applying a total amount of solution equivalent to 187 ml/m² (200 gal per acre). The pans were returned to the greenhouse and watered as before, and the injury to the plants as compared to those in control pans was observed after 14 days after spraying, and again, 27 days after spraying. After 14 and 27 days the post emergent herbicide activity was observed at a rate of application of 5.6 g/m². The data are shown in Table I. Example 4 Plant Growth Regulating Activity . The plant growth regulating activity of the compound of Example 1 was demonstrated by greenhouse testing. Established stands of fescue (Kentucky bluegrass No. 31) in pots having an area of about 100 cm (16 square inches) were trimmed to a uniform height. Duplicate pots were removed to a spraying chamber and sprayed by means of an atomizer as in Example 3. The application rate of the active ingredient was 0.56 g/m² (5 lbs. per acre) while applying a total amount of solution equivalent to 187 ml/m² (200 gal/acre). The pots were returned to the greenhouse and watered with the controls on a daily basis. After two weeks, the height of the grass was measured. The control pots grew an average of 199.58 mm over the two-week period, and the pots treated with the compound of Example 1 grew 80 and 90 mm, showing that the treated fescue had an average growth rate of 43% of the controls. The grass did not show any discoloration or other sign of phytotoxicity. Example 5 Preparation of Triisopropylamine Salt of 1,4,2-Oxazaphospholidine-4-Acetic Acid, 2-Methoxy-2-Oxide . The procedure of Example 1 is repeated except that 0.05 mol of triisopropylamine is substituted for the triethylamine used in Example 1. Analysis by spectral data indicates the presence of the desired triisopropylamine salt of 1,4,2-oxazaphospholidine-4-acetic acid, 2-methoxy-2-oxide. Example 6 Biological Activity . The compound of Example 2 and the compound of Example 5 is tested in greenhouse tests according to the procedure of Examples 3 and 4. Satisfactory results are achieved.

Claims: A compound represented by the formula: wherein R⁴ is an alkyl having from one to about four carbon atoms. A compound of Claim 1 wherein R⁴ is methyl. A compound of Claim 1 wherein R⁴ is ethyl. A compound of Claim 1 as the trialkylamine salt which is represented by the formula: wherein R¹, R² and R³ are individually selected from the group consisting of alkyl having from one to four carbon atoms. A compound of Claim 4 wherein R¹, R², R³ and R⁴ are independently selected from methyl or ethyl. A compound of Claim 4 wherein R¹, R² and R³ are ethyl and R⁴ is methyl. A compound of Claim 4 wherein R¹, R² and R³ are isopropyl and R⁴ is methyl. A herbicidal or plant growth regulant composition comprising a compound according to any of Claims 1 to 7 and an agriculturally acceptable diluent. A method of controlling the growth of plant species comprising applying to the plant species or to the plant locus an effective amount of a compound according to any of Claims 1 to 7.

Inventors: FIELDS DONALD LEE JR, GRABIAK RAYMOND CHARLES, FIELDS, DONALD LEE, JR., GRABIAK, RAYMOND CHARLES
Applicants: MONSANTO CO, MONSANTO COMPANY
Application year: 1989
Main classification: C07F9
IPC codes: C07F9, A01N57