NO121060B - - Google Patents

Description

Fungicides containing acorns

consists of a substituted benzoxazole,

benzothiazole or benzimidazole.

This invention relates to fungicidal agents containing

new organic thiocyanates and their use for combating fungal growth. The agents according to the invention are particularly suitable for combating fungi in industrial and agricultural processes and

- products.

Many industrial products, both during manufacture and

as a finished product, is normally exposed to fungal degradation if steps are not taken to prevent such degradation. Cellulose, starch and proteinaceous substances, animal hides, vegetable tanning fluids and leather are all damaged or degraded by the growth of fungi or other micro-organisms or by the enzymes produced by such growth. Wet cellulose containing more than approx. 30% humidity

is susceptible to attack by stain, mold and decay fungi. If these are not combated, the result is a loss of useful fibers in heavily cleaved cellulose, difficulties in dispersing partially cleaved cellulose, darkening and the development of undesirable odors due to the growth of micro-organisms. Different species of fungi form at different stages of leather production. For example, soaking is particularly favorable for the growth of micro-organisms, and even strong pickling solutions are susceptible to attack by some micro-organisms. Molds in particular can be troublesome and cause discolouration of the stained material, especially if it is kept for a certain time. During the chrome tanning process, the chrome-tanned material kept "in the blue" is highly susceptible to mold formation and discoloration; Mold growth can occur on strong, vegetable-tanned leather during the drying period and produces stains on either the flesh or hair side. When used for agricultural purposes, the preparations containing the organic thiocyanates can be used as seed, plant and soil fungicides to protect seeds, sprouts from seeds and plants against fungal attacks.

As for the amount of the organic thiocyanate

to be added to the aqueous system, suitable amounts vary from 0.5 to 1000 parts per million parts of moisture-free organic matter. It should be understood that larger quantities of the organic thiocyanate can be used without this having any harmful effect, but such larger quantities increase the costs without obtaining corresponding benefits.

Certain organic thiocyanates have been used quite extensively as insecticides (Donald E. H. Frear, Chemistry of the Pesticides, 3rd ed., D. Van Nostrand Company, Inc., New York, 1955), but many of these compounds which have shown themselves to be useful as insecticides, do not have significant fungicidal properties.

From Swedish patent no. 194,313 there are known fungicidal preparations containing 2-thiocyano-benzoxazoles, -benzothiazoles and -benzimidazoles.

The new compounds, which are used in the agents according to the invention and which can be defined as the S-thiocyanomethyl derivatives of 2-mercaptobenzothiazole, 2-mercaptobenzoxazole and 2-mercaptobenzimidazole, with the formula where X is 0, NH or S; however, has a greater fungicidal effect, especially against Chaetomium globosum.

The organic thiocyanates of formula (I) are prepared

in that a metal salt, preferably an alkali metal salt, and particularly preferably the sodium salt, of 2-mercaptobenzothiazole, 2-mercaptobenzoxazole or 2-mercaptobenzimidazole is reacted with chloromethylthiocyanate in an alcoholic solution. Since the reaction between the 2-mercapto compound and the chloromethyl thiocyanate is equimolar, it is usually preferred to use these two reacting components in approximately equal moles. The reaction can be carried out at relatively low temperatures.

The compounds of formula (I) are soluble in common organic solvents such as alkyl and aromatic hydrocarbons, alcohols, ketones, esters, ether alcohols, dimethylformamide, dimethylsulfoxide and other solvents. Addition of a surfactant to the liquid or to the solution makes the compounds more easily dispersible in water. In general, nonionic dispersants are preferred. Examples of such preferred nonionic dispersants include alkylphenoxypolyoxymethyleneethanol or alkylpolyoxyethyleneethanol. However, it must

time, it is understood that suitable dispersants are not limited to these.

The following examples shall serve to illustrate the preparation of the compounds used in the agents according to the invention and the fungicidal action of the agents.

Example 1

Preparation of 2-thiocyanomethylthiobenzothiazole Sodium 2-mercaptobenzothiazole used in this example was prepared by reacting 258.5 grams (1.54 mol) of technical 2-mercaptobenzothiazole with 102.8 grams (1.51 mol) of sodium ethoxide for about. 400 ml absolute, denatured alcohol (ethanol denatured with isopropanol and methanol). This solution was de-

cooled using an ice bath to keep the temperature below 40°C,

and treated with 162.4 grams (1.51 moles) of chloromethylthiocyanate.

The reaction mixture was kept at a temperature of 35 to 40°C overnight and then allowed to stand for a period of 15 days at room temperature. At the end of this period, the reaction mixture was filtered to remove the precipitated sodium chloride. The filter cake was washed first with denatured alcohol and then with methylene chloride. After pooling the filtrate and the denatured alcohol wash, an oily layer separated from the mixture. The oily layer thus obtained was dissolved in methylene chloride, and the resulting solution was mixed with the methylene chloride washing liquid, washed with water and dried with anhydrous magnesium sulfate. The methylene chloride was removed by evaporation to give 118.0 grams of 2-thiocyanomethylthiobenzothiazole as an oily liquid. An additional 242.1 grams of 2-thiocyanomethylthiobenzothiazole was recovered from the alcohol phase by extraction with methylene chloride. The alcohol phase was diluted with water and extracted three times with methylene chloride; the methylene chloride extracts were combined and dried over anhydrous magnesium sulfate. After evaporation of the methylene chloride, the 2-thiocyanomethylthiobenzothiazole remained as a residue, a product which could not be distilled without cleavage even at reduced pressure, or recrystallized. The infrared spectrum contained a strong band at 4.62 microns, indicating an organic thiocyanate.

Analysis: Calculated for CQH_N S_: N, 11.8; S, 40.3.

y d 2 j

Found: N, 11.0; S, 39.5.

Example 2

Preparation of 2-thiocyanomethylthiobenzoxazole

To a 250 mL three-necked, round-bottomed flask equipped with a stirrer, addition funnel, and thermometer, was added 150 mL of absolute ethanol and 2.3 grams (0.1 mole) of sodium. After the sodium had dissolved, 15.1 grams (0.1 mole) of 2-mercaptobenzoxazole was added, and the mixture was stirred until a homogeneous solution was obtained. The stirred reaction mixture was cooled, and 10.75 grams (0.1 mole) of chloromethyl thiocyanate was added dropwise. After the addition was complete, the reaction mixture was stirred at room temperature overnight and then poured into 1.5 liters of water and extracted with four 150 ml portions of ethyl acetate. The ethyl acetate extracts were combined and washed successively with a 500 ml portion of water, a 500 ml portion of two percent sodium hydroxide and a 500 ml portion of water. The ethyl acetate extract was dried over magnesium sulfate, and the ethyl acetate was removed under reduced pressure. The residue, a dark oil (14.1 grams, n 25 1.6372) represented a 63.5% yield of the crude product. A portion of this material was distilled under reduced pressure to give 2-thiocyanomethylthiobenzoxazole as a clear liquid,

k.p. 154-6 o C/0.2 mm Hg, n^ 25 1.6427). The infrared spectrum contained a strong band at 4.62 microns, indicating an organic thiocyanate.

Analysis: Calculated for CgH 6 N 2 OS 2 : S, 28.82.

Found: S, 29,30.

Example 3

Preparation of 2-thiocyanomethylthiobenzimidazole

A 500 ml four-necked, round-necked flask equipped with a stirrer, addition funnel, condenser and thermometer was charged with 300 ml of absolute methanol and 4.6 grams (0.2 mol) of metallic sodium. After the sodium dissolved, 30.0 grams (0.2 mol) of 2-mercaptobenzimidazole was added and allowed to dissolve, and then 21.5 grams (0.2 mol) of chloromethylthiocyanate was added dropwise over a period of time

in 5 minutes while the stirred solution was cooled. A light brown precipitate formed almost immediately, and the reaction mixture was stirred at room temperature overnight, then poured into two liters of water, and the solid was removed by filtration. The dried, crude 2-thiocyanomethylthiobenzimidazole, 35.1 grams

(79.4% yield) was recrystallized from toluene to give a pure sample of 2-thiocyanomethylthiobenzimidazole, m.p. 144-145.5°C.

Example 4

The effect of the organic thiocyanates compared to the effect of 2-thiocyanomethylbenzothiazole and 2-thiocyanobenzothiazole which is known as a fungicide from Swedish patent no. 194,313,

of three fungi, Aspergillus niger, Penicillium roqueforti and Chaetomium globosum, are determined in this example. The cellulose substrate method described in U.S. Pat. patent no. 3,193,448 was used for these samples.

The usual observation periods were after 7 and 14 days. Growth was noted after each period on the basis of the following scale:

4 = excellent

3 = good

2 = bad

1 = very poor, scarce, doubtful

0 = no growth.

The results are summarized in table 1.

Example 5

This example concerns a lap pulp preservation test that mimics the conditions prevailing during storage of moist mechanical lap pulp in pulp and paper mills.

The absorption mass conservation tests were carried out on a pulp substrate consisting of samples of spruce absorption mass with a weight of 2.5 + 0.1 grams each on an oven-dry basis and measuring approx. 6x6 cm. Each sample was placed in a sterilized glass Petri dish and the following series of operations were performed in duplicate for different concentrations of organic thiocyanates of formula (I).

1. An appropriate amount of the mineral salt was introduced into each sample of oven-dry absorbent mass by distributing 2.0 ml of the following solution evenly over the samples:

After the samples were evenly moistened, the entire series was

of samples dried in an oven at 105°C for one hour. The Petri dishes were kept partially open to facilitate drying.

2. Two milliliters of a solution or dispersion in water containing the organic thiocyanate dissolved in water to give the desired concentration in the sample was then added to the samples. Untreated control samples were prepared in duplicate by adding 2.0 ml of sterile water instead of the aqueous solution or dispersion of the compound to be tested. 3. The final addition to each sample was the inoculum containing 0.5 grams (0.5 ml) of water. The pulp samples thus contained 50% water and 50% pulp. The inoculation liquids were prepared in the following way. With the fungi Aspergillus niger, Chaetomium globosum and Pullularia pullulans, suitable spore suspensions were easily obtained from mycofil or maltagar slant cultures, which were carefully added to the upper side of the samples of recording mass. 4. A tight-fitting, wide rubber band was then placed over each Petri dish containing the inoculated recording mass sample to minimize the loss of moisture from the sample during incubation. The incubation temperature was 28-30°C.

The results are summarized in table 2, where the numerical values 0 to 4 have the same meaning as in example 4.

Example 6

By the method described in U.S. patent no. 2,881,070, column 5, line 12 to column 6, line 53, the effect of the compounds used in the agents according to the invention was investigated. The results are shown in the following tables 3 and 4.

The thiocyanates of formula I can be used diluted with

a carrier which may be liquid or solid. Dust can be produced with a finely divided, solid material such as talc, clay, pyrophyllite, diatomaceous earth, hydrated silicic acid, calcium silicate or magnesium carbonate. Optionally, wetting and/or dispersing agents can be used. When the proportions of these are increased, a wettable powder is obtained, which can be absorbed in water and used from a shower.

Dusts may contain 1% to 15% of one or more of the compounds of formula (I), while wettable powders may contain up to 50% or more of one or more of these compounds.

A typical composition of a wettable powder comprises 20 to 50% of the organic thiocyanate compound, 45 to 75% of one or more finely divided solids, 1 to 5% of a wetting agent, and 1 to 5% of a dispersing agent. Typical wetting agents include sodium dodecyl sulfate, sodium nonylbenzene sulfonate, sodium dioctyl sulfosuccinate, octylphenoxypolyethoxyethanol or other nonionic agents, such as ethylene and/or propylene oxide condensates with long-chain alcohols, mercaptans, amines or carboxylic acids. Typical dispersants include the sodium sulfonate of condensed naphthalene formaldehyde and lignin sulfonates.

Liquid concentrates can also be used. These are prepared by dissolving the organic thiocyanate of formula (I) in an organic solvent together with one or more surfactants. For example, one can mix 25 parts of one of the organic thiocyanate compounds, 5 parts of a surface-active, solvent-soluble alkylphenoxypolyethoxyethanol and 70 parts of one or more solvents, such as dimethylsulfoxide or dimethylformamide, or mixtures of these with xylene or other aromatic solvents.

The compounds of formula (I) can be used together with other fungicidal agents and also together with acaricides or insecticides or other pesticides.

Claims (1)

Fungicides containing or consisting of a substituted benzoxazole, benzothiazole or benzimidazole, characterized in that the substituted benzoxazole, benzothiazole or benzimidazole is a compound with the formula where X is respectively 0, S or NH.