GB2173193A - Bis-thiadiazole and bactericidal uses thereof - Google Patents

Abstract

The invention relates to a compound of formula <IMAGE> which is used as an active ingredient in bactericidal compositions.

Description

SPECIFICATION Bis-thiadiazole, methods for making it, and its use The present invention relates to the novel compound N, N' -methano-bis (2-amino-5-mercapto-1, 3, 4 thiadiazole) and the preparation thereof. This compound can be used as a bactericide in prevention and cure of plant bacterial diseases. This invention also relates to a bactericidal composition which contains said compound as an active ingredient. This kind of bactericide can be effectively applied in prevention and cure of bacterial diseases of plants such as bacterial blight of rices (Xanthomonas Oryzae).

Bacterial blight is one of the serious diseases of rices which is recognized worldwide to be difficult to deal with. It harms crops and causes severe reduction in production, especially in hybrid rice production.

Therefore, researching and screening for a high effectiveness, low toxicity, low residue type of new agricultural chemicals in dealing with the bacterial blight of rices has long been universally regarded as a very difficult problem to be tackled.

The bactericides SANKEL (Nickel N, N'-dimethyl-dithiocarbamate, C6H2NiN2S4) and PHENAZINE (Phenazine -5-oxide, C12hsONi) have a general curative and preventative effect on bacterial blight of rices and though the TF-128 (2-amino- i, 3, 4, thiadiazole) and DIKUBIS (N,N'-methano-bis (2-amino-l, 3,4-thiadiazole) have very good preventive and curing effects, owing to their toxicity they can hardly be accepted by the public. Some reports in Japanese Patent sho-4838141, sho-4911416 and sho-4911417 disclosed some new bactericides for curing and preventing of bacterial blight of rices. Although the toxicity was reduced, the preventive and curing effects were not ideal and these bactericides still haven't been commercialized.

The present invention provides a new compound which can be applied in prevention and cure of bacterial blight of rices. It has the following chemical formula.

The invention includes the salts of the compound, especially the alkali metal salts.

A process according to the invention for the preparation of this chemical compound comprises (i) treating the chemical compound of 2-amino-5-mercapto-1, 3, 4 -thiadiazole

with an alkali solution, preferably an aqueous solution of alkali metal hydroxide, a solution of alkali metal alcoholate, and an alcoholic solution of alkali metal hydroxide; (ii) adding to the reaction product of step (i) one or more of a formaldehyde solution; and an aqueous solution of polyformaldehyde to carry out a condensation reaction; iii) optionally, neutralizing with acid.

Any post-treatment can be carried out in a manner known per se.

The formulations of the bactericidal composition for preventing and curing of plant bacterial diseases comprise the compound of N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4- thiadiazole) of this invention as an active ingredient together with conventionally used adjuvants. The formulations may further comprise other active ingredients.

The bactericide in accordance with the present invention possesses the advantages of high effectiveness, low toxicity, low residue, safety, long life and is of the systemic type. The application of this bactericide not only provides a good preventive and curing effect as well as an increase in the yield of crops, but also is harmless to rice, fishes, humans and animals.

The bactericide in accordance with the present invention can be applied not only for preventing and curing of the bacterial blight of rices but also the cercospora spot of rices, cancer of citrus, bacterial wilt of groundnuts, bacterial wilt of tomato and other bacterial plant diseases.

The active ingredient of the bactericidial composition according to this invention is a novel chemical compound of N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4 - thiadiazole) having the formula

It has molecular formula C2H6N6H4 with molecular weight of 278.4, being white rectangular column shape crystal with melting point of 9Q+1 (Microscopic Method), it can easily dissolve in dimethyl formamide, and also in ethanol, acetone and dimethylsulfoxide.

The results of the elementary analysis of this compound are shown as follows: Calcd.: M.W. 278.4 C 21.57, H 2.17, N 30.19, S 46.06 Found.: M.W. 278.9 C 21.83, H 2.33, N 30.16, S 44.60 The instruments used for the identification of this compound are: HITACHI 340 UV-visible absorption spectrophoto-meter ZhD-01 S Spectro-Masspectrometer; MX-IE F.T. Infrared Spectrophotometer; CAMAC 250MH NMR Spectrometer.

In the process already outlined for making the compound the alkali metal hydroxide may be for example, sodium hydroxide, potassium hydroxide and the like; the alkali metal alcoholate may be, for example, sodium methanolate, potassium methanolate, sodium ethanolate, potassium ethanolate and the like; the polyformaldehyde may be, for example, triformol, paraformaldehyde and the like; the acide can be hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid and the like.

The results of the experimetns show that any of the aforementioned methods can provide the produce in accordance with the invention with a satisfactory quality and a good yield, but in view of the toxicity considerations and the cost of production, it is preferable to employ the aqueous solution of alkali metal hydroxide and formaldehyde solution as reactants. For example, the compound of 2-amino-5-mercapto-1, 3, 4-thiadiazole is treated with the aqueous solution of sodium (potassium) hydroxide, the resulting material is subjected to a condensation reaction by addition of formaldehyde, then the obtained produce may be neutralized with acid.

The reaction scheme is as follows:

A general example of procedure follows: The compound 2 amino-5-mercapto-1, 3, 4 thiadiazole and the aqueous solution of alkali metal hydroxide or the solution of alkali metal alcoholate, or the alcoholic solution of alkali metal hydroxide is added into a reactor equipped with a agitator and a reflux condenser. The molar ratio of the reactants 2 amino-5-mercapto-1, 3, 4 -thiadiazole: the alkali metal compound is 1: about 1-3, preferable 1: about 1-2.

The reaction can be carried out under room temperature with agitation, or under refluxing temperature with agitation, preferably under refluxing temperature with agitation if the aqueous solution of alkali metal hydroxide is used as reactant. For example, when the aqueous solution of sodium hydroxide is employed, the reaction is carried out preferably under refluxing at about llO"C for about 1-3 hours, them, the resulting product is concentrated, if necessary, the product is allowed to be cooled down to room temperature. Then, formaldehyde solution (37%) (or the aqueous solutions of triformol or paraformaldehyde) is added to carry out the condensation reaction.The molar ratio of the materials for the condensation reaction is 2 amino -5-mercapto -1, 3, 4, thiadiazole: formaldehyde (or triformol, paraformaldehyde) =1: about 0.3 -0.7, preferably 1: about 0.5. The condensation reaction can be carried out at the temperature between ambient temperature and about 100 C, preferably at ambient temperature of about 10-30"C.

The condensation reaction is conducted for about 1-2 hours, then, the resulting product is concentrated, subsequently neutralized by acid, the pH value of the obtained mixture is adjusted to a value below 6, preferably about pH 1-4, then filtered, washed with water and dried. The final product N'N-methano -5mercapto-1,3,4-thiadiazole is obtained.

In the above mentioned preparation procedure, after the reaction of 2 amino-5-mercapto-1,3,4- thiadiazole with the alkali metal compound is completed, the intermediate product of the alkali metal salt of N,N' -methano-bis (2-amino-5-mercapto -1, 3, 4-thiadiazole), for example, the sodium salt of N,N' -methano-bis (2 amino-5-mercapto-1, 3, 4-thiadiazole) represented by following formula, can be produced by the conventional methods.

The product is a light yellowish solid.

In the above mentioned preparation process, one of the initial raw materials is 2 amino-5-mercapto-1, 3, 4-thiadiazole represented by the structural formula

Its molecular formula is C2H3N3S2 with molecular weight of 133, it is a light yellowish needle like powder when in pure state, with melting point of 240"C, the solubility in cold water is poor, but it can dissolve in boiling water, alkalis, dimethy formamide (DMF), pyridine and the like. This compound is available on the market as an intermediate of the diuretic acetylazamide.The preparation processes of this compound have been already reported in the literature, for example, there are three different ways for the preparation of this compound:

It is found that a good yield and better quality of the product can be obtained by reacting aminourea with carbon disulfide.

The bactericidal compositions embodying the invention can be obtained by mixing N,N' -methano-bis (2-amino -5-mercapto-1,3,4 -thiadiazole) in accordance with the invention as an active ingredient, together with conventional adjuvants such as thickening agent, wetting agent, dispersing agent, emulsifier, penetrating agent, solvent, solid diluent or carriers and suitable synergist, and, if desired, the bactericidal composition can be made in various forms such as wettable powder, fluid formulation (colloid suspension), granule or water-soluble formation, etc.

The wettable powder formulation of the bactericidal composition may comprise the following: ingredients: N,N' -methano-bis (2-amino-5-mercapto-1, 3, 4 -thiadiazole) and other active components, if desired; neutral earth such as kaolinite, white clay, lieselguhr, expansion earth and the like; wetting agent such as detergent powder, nigre powder and the like. The wettable powder bactericide can be prepared by conventional methods such as mixing, grinding, etc.. The content of the active ingredient N,N' methano-bis (2-amino-5-mercapto-1, 3,4 -thiadiazole) in the wettable powder formulation of the bactericidal composition is 10%-90% by weight, preferably 15%-75% by weight.

The fluid formulation of the bactericidal composition may comprise the following ingredients: N,N' -methano-bis (2-amino -5-mercapto-1, 3, 4-thiadiazole) and other active components, if desired, dispersing agents, including anionic surfactant such as sodium methylene dinaphthalic sulfonate (NNO); thickening agents such as glycerine, ethylene glycol, poly (vinyl alcohol) etc. The preparation methods for fluid formulation of the bactericidal composition include: mixing and homogenizing all the components; further intensely grinding the mixture, for example, by using a colloidal mill. The fluid formulation of the bactericide composition in this invention employs N,N' -methano-bis (2-amino-5-mercapto-1, 3, 4-thiadiazole) as an active ingredient with a content of 10%-90% by weight, preferably 15%-75%, based on the total weight of the formulation.

It is found that the fluid formulation bactericide has a better preventative and curative effect than the wettable powder formulation bactericide.

The bactericide can be applied together with neutral or acidic fertilizers, pesticides or the like.

The inventors carried out animal toxicity tests on the bactericides which employ N,N' -methano-bis (2amino-5-mercapto-1, 3, 4-thiadiazole) as an active component (the tests include: acute toxicity, accumulate toxicity, chronic toxicity, sub-chronic toxicity, deformith foetus, mutation, carcinogenic test, three generations breed test, the thyroid gland function test etc., the total of 15 different study subtopics), and also carried out tests on its influence on environmental systems, on water, and on fish. Furthermore, tests on residual effects were also made. All results showed that the bactericide containing N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4-thiadiazole) has the properties of a low-toxicity, low residual and safe agricultural chemical.

The inventors have conducted a large number of tests on bactericidal effect. The results show that the bactericide of this invention can provide a good preventative and curative effect and a noticeable increase in crop yield. For example, the inventors employed a 25% wettable powder bactericide to carry out leaf surface-spray in a effective concentration of 0.025%-0.05% for 1-2 times. The sprays of the bactericide having been carried out in suitable period, the preventive and curing result ranged from 70% to 90% and the increase in out-put of crops ranged from 20% to 40%. The more significant preventative and curative effect can be obtained when the fluid formulation, e.g. colloidal suspension is appplied. Furthermore, the bactericide of the invention also has curing effect. The effect-remaining period is about 10-15 days.Moreover, a good result is also obtained when the bactericide in accordance with the invention is applied to a rice seedling bed.

Example I (The preparation of2-amino-5-mercap to- 1, 3, 4-thiadiazole) 49g of aminothiourea (with a content of 92.9%, 0.5 mole) was placed in a 500ml three necked flask which was equipped with a reflux condenser and a stirrer, then 120ml (1.5 mole) of DMF was added.

63.5ml (1 mole) of carbon disulfide was slowly poured into the flask. The mixture was slowly heated with a water bath with stirring. The reaction was carried out for 2.5 hours at a temperature between 40 and 60"C, then the reaction was continued for another 2 hours at a temperature of 70"C. After the reaction was completed, the DMF was distilled under reduced pressure. When the distillation was finished, 100ml of 20% sodium hydroxide solution was applied to dissolve the residue. After that, hydrochloric acid was added to neutralize the product to pH 1 and filtered, washed with water anddried. 51.9g of the product with a content of 97.0% was obtained, the yield was 76.33%.

Example II (The preparation of N,N'-methano-bis 12-amino-5-mercapto-l, 3, 4-thiadiazole)j 40ml of water and 12g of sodium hydroxide were placed in a 250ml three necked flask equipped with a and a reflux condenser. After the sodium hydroxide was dissolved in water with stirring, 27g of 2-amino5-mercapto-1, 3, 4-thiadiazole (0.2 mole, a purity of 98.7%) was added. The mixture was heated up to 110 C, for 1.5 hours. After the reaction was completed, the reaction mixture was slightly concentrated by heating and cooled down to room temperature of about 20-30 C, then 7.6ml of formaldehyde solution (0.1 mole, 37%) was added to the mixture and stirred at room temperature for 2 hours approximately.

Then small anount of water was distilled out under reduced pressure, subsequently the strong agitation was applied, then the product was acidified with 1:3 hydrochloric acid agueous solution to pH 1. The product was processed with filtration, water washing and drying in succession. 24.8g final product, with a content of 95.3% was obtained with a yield of 90.9%, m.p.190-192"C.

Example III 36g of sodium methanolate (30%) and 30ml of methanol were placed in a 250ml three necked flask equipped with a stirrer. The mixture was thoroughly mixed by stirring, then 14g of 2-amino-5-mercapto1, 3, 4-thiadiazole (95%. 0.1 mole) was added. After the dissolution was completed, 3.8ml formadenhyde (0.05 mole) was added. Then the reaction was carried out at ambient temperature for 1 hour with stirring.

The product was acidified with the 1:3 aqueous solution of hydrochloric acid to pH 1. Filtration, water washing and drying were conducted in succession. Finally, 10.5g of products was obtained with purity of 72%.

Example IV 6g of sodium hydroxide and 5ml of methanol were placed in a 250ml three necked flask equipped with a stirrer. After the dissolution was completed under stirring, 14g of 2-amino-5-mercapto-1, 3, 4-thiadiazole (0.1 mole, with a purity of 95%) and 3.8ml of formaldehyde (0.5 mole) were added. The reaction was carried out at ambient temperature with stirring for 30 minutes. Then, the reaction mixture was acidified to pH 1 with the 1:3 aqueous solution of hydrochloric acid. After that, the resulting product was subjected to filtration, water washing and drying, finally, 12.2g product, with a purity of 67.6%, was obtained.

Example V fpreparation of sodium salt of N,N' -methano-bis (2-amino-5-mercapto- 1, 3, 4thiadiazoleJ] 40ml of water and 12g of sodium hydroxide were placed in a 250ml three necked flask equipped with a stirrer, after the dissolution was completed by stirring, 29g of 2-amino-5-mercapto-1, 3, 4-thiadiazole (0.2 mole, with a purity of 92.07%) was added. The mixture was heated up to about 110 C for 1.5 hours, then the mixture was concentrated and cooled down to room temperature again, 7.6ml of formaldehyde (0.1 mole, 37%) was added, the condensation reaction was carried out for 2 hours, after that, the resulting mixture was subjected to concentration and the solid light yellowish intermediate product was obtained.

Example Vl {formulation and preparation of wettable powder bactericidal composition) Formulation: N,N'-methano-bis (2 amino-5 mercapto-1,3,4 thiadiazole) 25 parts White clay 70 parts Sodium dodecylphenyl sulfonate 5 parts 100 parts Preparation: 25g of N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4-thiadiazole) and 70g of white clay, 5g detergent powder were mixed together, thoroughly ground in an agate mortar so that all the mixture passed 200 mesh sieve, then 100g of wettable powder bactericidal composition with an active component content of 25% was obtained.

Example VII (Formulation and preparation of fluidable bactericidal composition Formulation: N,N'-methano-bis (2 amino-5-mercapto-1 3,4-thiadiazole) 15parts water 75parts NNO (sodium methylene dinaphthalic sulfonate) 7parts Glycerine 3parts 100 parts Preparation.

7g of NNO and 75g of water were added into a mixer equipped with a stirrer, after NNO was completely dissolved in water, 39 of glycerine and 15g of N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4-thiadiazole) were added. After thorough stirring, glass beads were added in to conduct the grinding under strong stirring for 10 hours, finally the glass beads were filtered out, the fluidable formulation in accordance with the invention was obtained.

Example Vlil (Comparison of effect of different formulations) formulation Concentration Preventive and p. p. m. curing effectiveness(%) 25% wettable powder 1000 59.90 20% fluidable formulation 1000 78.06 Example IX (The curing effects) The test specimen rice was "Nanking No.11", the bactericide was applied on the specimen rice at the late boot stage, the spray-area was 33.3 M2. The bacterial blight of rice was induced by artificial inoculation before the bactericide was applied. The concentration of the bacterium solution was 4 million/ml.

The leaf surface-spray was carried out on the third day after the innoculation. The results of the curing show as follows: (Field test, by Agricultural College of Anhui Province) Effective on the 25th after spraying Bactericide concentration Incidence of Parameter of Curing effecti p. p. m. disease(%) state of veness {%) disease { /0) Wettable pow der[containing N,N'-methano- 250 11.9 4.7 72.7 bis(2 amino mercapto-1,3,4 thiadiazole] Same as above 500 8.8 2.5 85.8 Phenazine-5 oxide powder 500 18.7 5.0 70.2 (from Japan) DICUBIS powder [containing N, 125 22.8 5.9 66.7 N'-methano-bis (2-amino-1,3,4 thiadiazole] Blank - 42.4 17.7 The results of the tests show that the curing effectiveness of the bactericide containing N,N'-methanobis (2-amino-5-mercapto-1, 3, 4-thiadiazole) as an active ingredient with the concentration of 500 p.p.m.

still has a very high-remaining percentage of 85.8% after 25 days. The curing effect of bactericide of this invention is obviously better than that of phenazine-5-oxide powder, and similar to that of DICUBIS powder containing N,N'-methano-bis (2-amino-1, 3, 4-thiadiazole).

Example X (The preventive effectiveness) The test specimen rice was mid-long-grained nonglutious rice "Nanking No.11", the leave-surface spray on a test area of 13.3 M2 was carried out firstly, then the bacteria was inoculated. The results are shown in the following table.

(Field test, by the Agroscience Research Institute of Yizhen Prefecture, Jiansu Province) Bactericides Effective Inspections on the 11th day for treatment concentration after the inoculation Incidence of Parameter preven diseases % of state effecti of disease ve effec tiveness % Wettable powder [containing N,N' -methano-bis (2 0.05 5.0 1.3 97.8 amino-5 mercaoto -1,3,4 thiadia -zole)] Phenazine-5 oxide powder 0.05 87.5 35.0 41.2 (From Zhe Jiang Province, China) Phenazine-5 oxide powder (from the city 0.05 97.5 45.0 24.4 of Tian jing, China) DICUBIS powder [containing N,N' -methano-bis (2 0.0125 7.5 1.9 96.8 amino-5 mercapto -1,3,4 thiadia zole)] Blank - 95.2 59.5 The results show that the bactericide of this invention has a high preventative effectiveness of 97.8% at an effective concentration of o.05%. The preventative effectiveness of the bactericide of this invention is similar to that of DICUBIS powderwith low concentration, and clearly superior to that of phanazine-5oxide which mainly possesses preventive effectiveness. It has been found that the preventative effectiveness of the bactericide in accordance with the invention had a duration of more than 20 days.

Example Xl (test of crop yield) Bactericides 0- 10- 20- 40- 60- 80- 100- Total Average 10 20 40 60 80 100 120 times increase Wettable powder[con taining N,N'-methano -bis(2 amino-5-mer- 0 7 19 3 2 0 - 31 31.1 capto-1,3,4 thiadia zole)] with the effective concentra tion of 0.025-0.1% DICUBIS powder [con taining N,N'-methano -bis (2 amino-1,3,4 4 14 31 15 5 1 2 72 36.2 thiadiazole)] with the effective concen -tration of 0.0125 0.025% Note: leaf surface-spray, applied twice.

The results of plot and big area tests show that the increase in crop yield is obtained by employing the bactericide of this invention on the blight of rice. The average increase rate is up to 31.1%, which approaches the effect of DICUBIS, and the increase rate in the yield apparently trends towards a concentration between 20-40%.

Claims (19)

1. A chemical compound of N,N'-methano-bis (2-amino-5-mercapto-1, 3, 4-thiadiazole) represented by the formula

and salts thereof.

2. A process for preparing a compound of claim 1 represented by the following chemical formula

which comprises treating the chemical compound of 2-amino-5-mercapto-1, 3, 4-thiadiazole

with an alkali solution adding one or more of a formaldehyde solution, or an aqueous solution of polyformaldehyde to carry out a condensation reaction; and optionally, neutralizing with an acid.

3. A method according to claim 1 wherein the alkali solution is at least one of an aqueous solution of alkali metal hydroxides, a solution of alkali metal alcoholate, and an alcoholic solution of alkali metal hydroxide.

4. A method according to claim 3 wherein said alkali metal hydroxide is sodium hydroxide or potassium hydroxide; said alkali metal alcoholate comprises sodium methanolate, potassium methanolate, sodium ethanolate or potassium ethanolate; said alcoholic solution of alkali metal hydroxide is methanolic solution of sodium hydroxide, methanolic solution of potassium hydroxide, ethanolic solution of sodium hydroxide or ethanolic solution of potassium hydroxide.

5. A process according to claim 2, claim 3 or claim 4, wherein said polyformaldehyde comprises triformol or paraformaldehyde.

6. A process according to any one of claims 2 to 5, wherein said acid is hydrochloric acid, sulfuric acid, phosphoric acid or acetic acid.

7. A process according to any one of claims 2 to 6, wherein the reaction temperature of the treating step is in the range from abient temperature to refluxing temperature.

8. A process according to any one of claims 2 to 7, wherein the reaction temperature of the condensation reaction is in the range from ambient temperature to approximately 100"C.

9. A process according to claim 8, wherein the reaction temperature of the condensaiton reaction is ambient temperature, approximately 10-30"C.

10. A process according to any one of claims 2 to 9, wherein the pH value after neutralization is below 6.

11. A process according to claim 10, wherein the pH value is below 4.

12. A process according to any one of claims 2 to 11, wherein the molar ratio (compound of formula (all)): said alkali formaldehyde (or polyformaldehyde) is (1: about lto about 3:about 0.3 to about 0.7).

13. A process according to claim 13, wherein the molar ratio of chemical compound of formula (lI):said alkali formaldehyde (or polyformaldehyde) is 1:about 1 to about 2:about 0.5.

14. The use of the compounds claimed in claim 1, in the prevention or cure of the bacterial diseases of plants.

15. Bactericidal compositions for prevention or cure of bacterial diseases of plants, which comprise the compound as defined in claim 1 as an active ingredient, and may further comprise other active components and conventional adjuvants.

16. Method of applying the compounds claimed in claim 1 for preventing or curing bacterial diseases of plants, which comprises applying a suitable form of bactericidal composition containing an effective amount of chemical compound of formula (I) to the plants or their environment.

17. The method of applying chemical compound of formula (I) for preventing and curing the bacterial diseases of plants according to claim 16, wherein the bactericidal composition is in the form of a wettable powder or fluid formulation.

18. Methods of preparation of the compounds of claim 1 substantially as herein exemplified.

19. Methods of treatment of plants substantially as herein exemplified.