DE2525023A1 - N-Halophenyl isoxazole-4-carboxamides - are fungicides useful in plant protection - Google Patents

Abstract

Isoxazoles of formula (I) are new: (where in formula (I) X is halo; Y is H or halo). They are prepd. from the corresp. halo-substd. acetanilide by reaction with (a) an alkyl orthoformate then (b) NH2OH. Cpds. (I) most esp. the dichlorinated cpds., are useful as fungicides for plant protection.

Description

New tsoxazole derivatives. Process for their preparation and fungicides containing these compounds The invention relates to new isoxazole derivatives of the general formula wherein X is halogen and t is hydrogen or halogen.

The process for the preparation of the compounds I according to the invention is characterized in that acetessiganilides of the general formula II are used in which X and Y have the meaning given above, with orthoformic acid esters of the general formula HC (GR) 3 III in which R can be a lower alkyl radical, preferably the methyl or ethyl radical, and excess acetic anhydride is converted and the 2-alkoxymethylene acetoacetic anilide formed in this way is the general formula wherein X, n and R have the abovementioned meaning, cyclized with an at least equimolar amount of hydroxylamine to give the isoxazoles I.

The last-mentioned reaction is carried out in organic solvents with or without the addition of water, lower alcohols being preferred as organic solvents. The reaction temperature can be between 0 ° and 1000C, preferably between +100 and + 500C. The course of the reaction can be seen from the following equations: Equation 1: The 2-alkoxymethyleneacetessiganilides required as precursors for the preparation of the compounds I according to the invention are aeu.

The establishment of a single representative of compound class IV, the 2-ethoxymethyleneacetessiganilide from acetoessiganilide, triethyl orthoformate and acetic anhydride is from G.

Kempter, W. Schmidt and H. Dost, Chem. Ber. 98, 955-961 (1965) been. Table 1 shows the new 2-ethoxymethylene aceto acetic anilides.

The isoxazoles I are also new. Only three isoxazoles with X = H, 2-CH3 and 4-CH3 are available from F.B.

Dains and EL Griffin, J. Am. Chem. Soc. 35, 959-976 (1913). The production of these isoxazoles took place in poor yields according to the following topic: X = H, 2-CFI3, 4-CH3 After separating the unusable by-product, the authors obtained between 20 and 40% yield of 2-arylamino-methylene-acetoacetic anilides, which were cyclized with hydroxylamine hydrochloride / pyridine in boiling ethanol: Surprisingly, according to the method according to the invention, the easily accessible 2-ethoxymethylene aceto acetic anilides were cyclized with hydroxylamine to give the isoxazoles even at room temperature and below in yields between 90 and 100%.

The isoxazoles synthesized are listed in Table 2.

While the known compounds are practically ineffective fungicidal, the compounds of formula I can be used as fungicides in crop protection. Preferred of them are the dihalogenated, especially the dichlorinated compounds.

Example 1: 2-ethoxymethylene acetic acid 3,4-dichloroanilide 1.0 Mol (246 g) of acetoacetic acid 3,4-dichloroanilide are mixed with 1.12 mol (166 g) of triethyl orthoformate and 2.97 moles (302 g) of acetic anhydride refluxed for 1.5 hours. After cooling down to room temperature is sharply suctioned off from the precipitated crystals and with a 1: 2 mixture of benzene / gasoline. The product is for further implementation pure enough.

Yield: 251 g tS 83% of theory Th.

Melting point: 124 ° -125 ° C. Melting point after recrystallization from benzene: 1250 ° -1260 ° C. C15H15Cl2NO3 MW 302.15 calc .: C 51.7%; H 4.3%; N 4.6% Found: C 51.8%; H 4.1%; N 4.5% The compounds listed in Table 1 were prepared analogously.

In the case of easily soluble 2-ethoxymethylene aceto acetic anilides, under certain circumstances the reaction mixture can be concentrated by distillation.

Example t: 5-methyl-isoxazole-4-carboxylic acid-3,4-dichloroanilide 0.11 Mol (7.65 g) of hydroxylamine hydrochloride are dissolved in 30 ml of water with an ice cold Solution of 0.11 mol (4.4 g) sodium hydroxide in 20 ml of water and mixed with 150 ml of methanol diluted. Then with 0.1 mol (30.2 g) of 2-ethoxymethylene acetoacetic acid-3,4-dichloroanilide offset and about 4 hours stirred at room temperature. Then cools one to + 50C, sucks off and washed with water. After drying in air, one obtains colorless crystals.

Yield: 26.4 g # 97.5% of theory Th.

Melting point: 1450C Melting point after recrystallization from methanol: 1460C C11H5Cl2N2O2 MG mg 271.1 calc .: C 48.7%; H 3.0%; N 10.3 ffi Found: C 48.6%; H 3.0%; N 10.2 % The compounds listed in Table 2 were prepared analogously.

Table 1: No. X Fp. (° C) a 2-Cl 95-96 b 3-Cl 98 c 4-Cl 139.5 d 2,4-C12 127 e 2,5-Cl2 146 f 3,4-C12 # 125-126 g 3,5-Cl2 131 h 3-Br # 118 i - 4-Br 124 k 4-F 127 1. 2,5-Br 140 m - 3-J 148 Table 2: No. X Fp. (° C) 1 2-C1 111-112 2 3-C1 106-107 3 4-C1 151 4 2,4-Cl2 120-121 5 2,5-C12 122 6 3,4-C12 145 7 3,5-C12 182-183 8 3-Br 122 9 4-Br # 162-163 10 4-F 117-118 11 2,5-Br 171-173 12 3-J 148-149 Example 3: Vine plants were treated in the 3-leaf stage with the claimed compound no. 6 in the application rates of 500, 250, 125, 60 and 30 mg active ingredient / liter of spray mixture on the underside of the leaves. The comparison agent used was N-trichloromethanesulfenyl phthalimide, which was used in the same active ingredient concentrations.

The plants were first placed in a greenhouse at 240C for 3 weeks and 60% relative humidity. After that, they were infected with the pathogen's spores powdery mildew inoculated on the grapevine (Plasmopora viticola), 4 hours kept at a temperature of 200C and a relative humidity of 100% and then put back in a greenhouse with the above conditions.

To the eruption of the grass of spurs on the underside of the leaves stimulate, the plants were 6 days later again for 24 hours in a Climate chamber with 100% relative humidity and 200C. After the outbreak of the The tests were evaluated for spores in the untreated, infected plants for infestation with Plasmospora viticola.

The degree of infestation was expressed as a percentage of infested leaf area on untreated, infected plants (= 100? jo infestation).

Table p % Infestation with Plasmospora viticola Compound # at mg active ingredient / i.tr. Spray mixture No. 500 250 125 60 30 6 0 0 3 5 15 compensation means 0 3 5 15 25 untreated, infected 100 plants As can be seen from Table 4, Compound No. 6 shows one of the comparative agents. superior fungicidal effect in long-term tests against Plasmo-pora viticola.

Claims (4)

PATENT CLAIMS Isoxazole derivatives of the general formula wherein X is halogen and Y is hydrogen or halogen. 2. A process for the preparation of the isoxazoles of the general formula 1, characterized in that acetoacetanilides of the general formula are used in which X and Y have the meaning given in claim (1), with orthoformic acid esters of the general formula SC (OR) 3 III in which R is a lower alkyl radical, and acetic anhydride to form 2-alkoxymethylene acetoacetic anilides of the general formula and these cyclized with hydroxylamine to give isoxazoles I. 3. Plant protection products, characterized by a content of compounds of the formula I in combination with the usual formulation auxiliaries. 4. Use of compounds of the formula I for combating plants Fungal diseases.