IL35262A - 2-chloroethylphosphonothioic acid,its and esters thereof - Google Patents

Description

NOVEL 2-CHLOROETHYLPHOSPHONOTfflOIC ACID, ITS TRITHIOIC ACID AND ESTERS THEREOF This invention relates to novel 2-chloro-ethylphosphonothioic acid, its trithioic acid and esters thereof which are useful as plant growth regulators and processes for their preparation.

It is known that certain phosphorus-containing compounds are useful as plant growth regulators. One of the most important phosphorus compounds of this type is 2 -chloroethyl=phosphonic acid which has found importance as a plant. growth regulator, particularly in the treatment of pineapples, soybeans, and other products.

According to the present invention, it has been found that a new class of phosphorus compounds related to 2-chloroethylphosphonic acid have completely unexpected. One of the primary characteristics of the products of this type resides in the presence of the 2 -chloroethyl group as this is important to the plant growth stimulating activity because it is believed that the action of the compound on the plant is due to the fact that they are absorbed by the plant and release ethylene, a known plant regulator, in a form which can be used by the plant. The compounds of the present invention have now been found to. have this characteristic.

The present invention provides plant growth regulators of the formula: wherein X oxygen or sulfur, and R is hydrogen, arlkylr- -f ronr ctbonr -1-te--5- -oa-r-bo-R -aterns-,-aryl of about 6 to 12 carbon atoms, preferably phenyl, alkaryl of about 7 to 15 carbon atoms, preferably tolulyl and xylyl, and-ar-a-l-k--l--©f abeu-t--7--to-15-ea-r cm- -a-fe msτ -pref-er-abiy-benz l-. The invention further provides a process of applying these materials to plants in the presence of a carrier to regulate the growth characteristics of the plants. It further provides a method for It has been found that the above identified 2-chloroethylphosphonothioic acids, tri-thioic acids and ester derivatives thereof have unique activity as plant growth regulators and may be applied to plants such as pineapples, soybeans, tomatoes, small grains and the like to regulate growth and thereby improve crop yields. Thus these compounds may be stated to be plant growth hormones as they operate to increase yields of products of these types.

The compounds of this invention are soluble in varying degrees in water and so they can be applied to the plants in aqueous solutions composed wholly or partially of water; partial solutions include those formed of water and say acetone or methyl ethyl ketone. Any aqueous medium may be used provided that it is not toxic to the plant. Where any particular derivative is less water soluble it may be solubilized by the use of co-solvents and, the like. Also the compounds may be absorbed on solid carriers such as vermiculite, attaclay, talc and the like for application in granular form. Dusts may also be used in which case the active ingredient will be diluted with clays or other powders for example pyrophyllite, diatomaceous earth and long as a effective amount is applied. It is preferred to apply the compound in a concentration of about one-half to ten pounds per acre or higher depending on the particular derivative .used. A preferred rate of application ranges from 2 to 5 pounds per acre. The phosphonic derivatives need only be applied to the plant in low volumes of water to achieve satisfactory flower initiation and this is an important advantage of this invention. Whereas it is usually necessary to apply the known agents in large volumes of water, say on the order of 200 to 400 gallons per acre and even up to 1,000 gallons per acre in the case of ethylene to achieve flower initiation, it is possible to apply a compound of this invention in far lower volumes of water and still achieve satisfactory flower initiation. For. example, the compounds in this invention can be applied in 50 gallons of water at the rate of ί pound per acre to achieve 100% flower induction on pineapples of the Smooth Cayenne variety. The ability to apply the active agent in a reduced volume of water is an important agronomic advantage because a larger acreage of plantation can be treated before recourse to a water supply is necessary, smaller equipment can be used and costs can prepared by the reaction of certain acid halide intermediates with appropriate reagents. A basic starting material is preferably the corresponding acid halide of the following formula: wherein Hal is a halogen and preferably chlorine.

In the first step of the process, this acid halide is reacted with phosphorus pentasulfide at a temperature of about 150° -175°C. for several hours. A molar excess of about 2:1 to 6:1 over the acid halide is generally employed. On completion of the reaction, distillation of the product will provide the 2-chloroethylphosphonothipic dihalide of the following formula: . wherein Hal is as above.

This thioic dihalide is then subjected to aqueous hydrolysis by reaction with an excess of water to prepare the thioic acid where X is oxygen and R is hydrogen. This reaction is conducted by mixing the thioic dihalide with a solvent (e.g. a agitating while heating at about 40-75°C. for about 1 to 5 hours. Removal of the solvent and excess water provides the 2-chloroethylphoephono-thioic acid of the formulat S CL CHJCHJ - P - OH OH The corresponding 2-chloroethylphos- phonotrithioic acid is prepared by reaction of the 2-chloroethylphosphonothioic dihalide with hydrogen sulfide in place of water.

Using the same reaction conditions the starting material is charged to the solvent and HjS is passed or bubbled through at a steady rate to prepare the trithioic acid of the formula.

The esters and thioesters of the com- pounds of this invention, wherein X is O or S and R is alkyl, aryl, alkaryl or-¾ralky3r, are obtained by the reaction of the appropriate alhosphono cohol or. thioalcohol with the 2-chloroethylp¾ thioic dichloride in the presence of an organic or inorganic base which acts as an acid acceptor. ethanol, normal-propanol, isopropanol, normal- butanol, normal-pentanol, methylthiol, ethyl- thiol, n-propylthiol, n-butylthiol, phenol, toluene toluene xylene thiophenol, tolaoi, thic xrlnial, -xylol, thio-xylene -^-lr&l, benzyl alcohol, benzylthiol and the like.

Equivalent materials may also be employed in this reaction.

As indicated, this reaction is con¬ ducted in the presence of an acid acceptor such as an organic or inorganic base, suitable bases being the inorganic bases such as the alkali metal hydroxides, for example NaOH, KOH, etc., alkali metal carbonates such as sodium carbon¬ ate and potassium carbonate, alkali metal bi- N aHCOg carbonates for example - aCHO^ and KHCO3 as well as the alkali earth, metal hydroxides, carbonates, and oxides. Organic bases may also be employed, preferably the organic amines such as the tri- alkyl amines, triaryl amines, heterocyclic amines, and the like including triethy-^jamine, trimethyl — amine, pyridine and mixtures thereof. Obviously, any equivalent basic material may also be employed.

In preparation of the ester or thio- ester, the 2-chloroethyl phosphonothioic dichloride is charged to a solvent solution and preferably a aspect include diethylether , dioxane, petroleum ether, aromatic hydrocarbons, for example benzene, toluene, xylene etc as well as mixtures thereof. After charging the thioic dichloride to the ether solution, a solvent solution containing the alcohol or thiol and acid acceptor is then added to the thioic dichloride. As two moles of alcohol or thiol are to be employed in the reaction per mole of thioic dichloride, and 2 moles of acid acceptor are also employed, the preferred molar ratio of materials of the 2-chloroethylphosphonothioic dichloride, alcohol or thiol and acid acceptor are preferably about 1:2:2, although variations may be used with equivalent results.

In conducting the reaction, the above materials are charged to a suitably equipped reaction flask at a temperature of about -10° C to +10°C. and the solution is stirred while allowing the temperature to increase, slowly without the use of external heat or cooling. Generally therefore the temperature, while conducting the reaction, will range from about -10eC. to 35eC. After no further rise in temperature is noted, the precipitated salt is removed by filtration following formula: Cl CH CH = P - XR wherein X and R are as defined above.

The following examples are provided to illustrate the products and processes of the invention.

EXAMPLE I 2-Chloroethylphosphonothioic Dichloride A 200 ml flask equipped . with stirrer, thermometer, reflux condenser and drying tube was flushed with dry nitrogen. There was then charged 90.8 grams (o.5 mol) 2-chloroethylphosphonic dichloride and 26.7 grams (0.12 mol) phosphorus pentasulfide (Fisher Scientific Co.). The mixture was stirred and heated to 155-160eC. for 12 hours. The resulting product was isolated by distillation from the crude reaction mixture. There was obtained 57.1 grams of material boiling at 35-36° C. at 0.25 mm pressure. The refractive index at 25°C. was 1.5658.

Analysis Calc 'd. Found EXAMPLE II 2-Chloroethylphoaphonothioic Acid Cl-CHjCHj - P-OH A charge of 12.0 grams (0.066 mole) 2-chloroethylphosphonothioic dichloride (from Example I), 25 ml. acetone, and 110 ml water was magnetically stirred at 50eC. for 2 hours. The water solution was then filtered from the re¬ sulting mixture to free from some cloudiness and the filtrate flash evaporated. to constant weight.

There was obtained 9.1 grams of product.

Analysis Clc 'd. Found C2H6C102PS %S 19.97 18.20; 18.33 EXAMPLE III 2-Chloroethylphosphonotrithioic Acid ' S Cl CHjCHj - - PII - SH SH The reaction of Example II was repeated except that an excess of HjS was bub ed through o the solution at 50 C. for 1 hour in place of add¬ ing water. The excess gas was then removed and the filtrate flash evaporated to recover 8.6 grams of product.

EXAMPLE IV 2-chloroethylphosphonothioic dichloride and 150 ml dry ether was cooled to 0°C. and 0-5°C.

There was added a solution of 18.8 grams (0.2 mol) phenol and 20.2 grams (0.2 mole) triethylamine in 150 ml dry ether.

After the addition was completed, the solution was stirred for one hour while the temperature slowly increased to 28°C. The precipitated triethylamine hydrochloride was removed by fil-tration and washed with dry ether.

The filtrate was flash evaporated to constant weight. There was obtained 29.9 ,grams of amber liquid product.

EXAMPLE V There was charged 19.8 grams (0.1 mol) 2-chloroethylphosphonothioic dichloride and 150 ml dry ether. At 0-5eC. there was added a solution of 22.0 grams (0.2 mol) thiophenol and 20.2 grams (0.2 mol) triethylamine in 150 ml dry ether. After stirring one hour while warming to room temperature the triethylamine hydrochloride was filtered off and washed with dry ether. Flash evaporation of the filtrate yielded 33.9 grams of

Claims (7)

WHAT WE CLAIM IS s

1. A compound of the formulas wherein X is oxygen or sulfur and R is hydrogen, arkyl-ef-ir^-Hr-earbon-trtxmjs-i aryl of 6 to 12 car¬ bon atoms, alkaryl of 7 to 15 carbon atoms -osr ar-alkjtl--of-7-to--1-5--oa-rfeon-stems-*--

2. The compounds claimed in Claim 1, wherein X is oxygen and R is hydrogen.

3. The compounds claimed in Claim 1, wherein X is sulfur and R is hydrogen. 4-.—The-eempetmds--c-lrairaed- ifv-Cia-inv-1, wherein--X--is--oxygen- -and -R-is -methyl,

4. -&.- The compounds claimed in Claim 1, wherein X is sulfur and R is phenyl.

5. The compounds claimed in Claim 1, wherein X is oxygen and R is phenyl.

6. --7-.- A method for regulating the growth of plants which comprises applying to the plant a composition comprising an effective amount of a compound claimed in Claim 1 in association with a carrier whereby the compound is absorbed by the plant to release ethylene to the plant. 6

7. The method claimed in Claim 7-, wherein the carrier is water, a partial solution of water 35262/2 7 "θ -- 8· The method claimed in Claim- &·,- wherein the composition is applied to the plants at a rate of one half to ten pounds per acre. -i-0 9. A process for the preparation of a compound of the formula - S C1 CH CH_ - P - XH XH wherein X is. joxygen or. sulfur- which comprises reacting a chloroethyl-phosphonothioic dihalide with water or hydrogen sulfide at a. temperature of 40 -75°C. A process for the preparation of a compound of the formula S II XR wherein X is oxygen "or aryl of 6 to 12 carbons, 15 carbon atoms which comprises reacting. 2 -chloroethylphosphono-thioic dihalide with a compound of the formula RXH, wherein X and R are as above, in the presence of an acid acceptor at a temperature of about -10 to 35°C. . growth 12r 1 1. * A plant/ regulating composition of matter comprising an effective growth stimulating, flower initiating or crop increasing amount of a compound of the formula: S if CI CH CH - P - X 2 2 t XR wherein X is oxygen or sulfur and R is hydrogen or phenyl, and a carrier therefor, 11 43s- 12. A composition as defined in claim 12 wherein said carrier 35262/2 11 . 44,- 13. A composition as defined in claim 4-3- wherein said carrier is a solid material. -&.- 14. A method for regulating the growth of plants which comprises applying thereto an effective growths re ulating amount of a composition as defined in claim ς 11. . 14 •16»-- 15. A method as defined in claim -1-5- herein said composition is applied at a rate of about 0.5 to 10 lbs. of said compound pe acre of plants. ■17 - 46. A method for regulating the growth of plants which comprises applying thereto a compound having the formula as 11 defined in claim 12-at a rate of about 0.5 to 10 lbs. per acre of plant, S. HOROWITZ & CO. AGENTS FOR APPLICANTS