CA1092109A - 1,2,4-oxadiazin-5-one derivatives - Google Patents

Abstract

ABSTRACT
The hitherto unknown 1,2,4-oxadiazin-5-one derivatives of the formula:

Description

THIS INVENTION relates to new derivatives of 1,2,4-oxadiazin-5-one and to processes for their preparation.
The new derivatives of 1,2,4-oxadiazin-5-one of the present invention are those compounds of the general formula:

R

O~ N

~ ~ Ar wherein R represents a hydrogen atom or an alkyl radical ~ containing 1 to 4 carbon atoms, or a phenyl radical, and : 10 Ar represents a phenyl radical substituted by 1, 2 or 3 substituents, which - when two or three substituents are present - may be identical or different, selected from halogen atoms, the hydroxy radical, alkyl radicals containing 1 to 4 carbon atoms, alkoxy radicals containing 1 to 4 carbon atoms, alkylthio radicals containing 1 to 4 carbon atoms, alkylsulphonyl radicals containing 1 to 4 carbon atoms, the trifluoromethylthio radical, the nitro radical, dialkylamino radicals containing 1 to 4 carbon atoms in .,~

o~

each alkyl group, the sulphamoyl radical and dialkylsulphamoyl radicals containing 1 to 4 carbon atoms in each alkyl group, or Ar represents a thienyl, pyrrolyl or furyl radical unsubstit~lted or substituted by a halogen atom or an alkyl radical containing 1 to 4 carbon atoms.
Preferred compounds of the invention are those 1,2,4-oxadiazin-5-ones of general formula I wherein R represents a hydrogen atom or a methyl or phenyl radical, and Ar represents the phenyl radical substituted by 1, 2 ox 3 substituents selected from halogen atoms and methyl, hydroxy, methoxy, methylthio, methylsulphonyl, trifluoromethylthio, nitro, dimethylamino, sulphamoyl and dimethylsulphamoyl radicals, or Ar represents a thienyl, pyrrolyl or furyl radical unsubstituted or substituted by a halogen atom or the methyl radical.

.. j, .
,~ .

~0'3Z~D~

Of outstanding importance are those l,2,4-oxadiazin-S-one derivatives of general formula I wherein Ar is a thienyl radical optionally substituted by a halogen atom or an alkyl radical containing 1 to 4 carbon atom~, for example 3-(5~chlorothien 2-yl)-5,6-dihydro 4H-1,2,4-oxadiazin-5-one, 3-(thien-2 yl)-5,6-dihydro-4H,l,2,4-oxadiazin-5-one, 6-methyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5~one, 3-(thien-3-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, 3-(5-methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, 3-(3-methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, 3-(3-bromothien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, 6-ethyl-3-~thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, and 6-phenyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.
; lS According to a feature of the present invention, ; the compounds of general formula I are prepared by the process which comprises cyclising an amidoxime derivative of the general formula:

~ . . , ~ ., .~i~- ~
~ s~, 10~2~

R

. Ar - \ . II

wherein Ar and R are as hereinbefore defined, and Rl represents an alkyl radical containing 1 to 4 carbon atoms.
Generally the cyclisation is carried out by ¦ heating the amidoxime derivative in a basic medium at ¦ temperature between 20 and 70C. It is particularly ¦ advantageous to work in an organic solvent, such as pyridine or in an alcohol such as ethanol, in the presence of an alkali metal alkoxide such as sodium methoxide or sodium ethoxide.
The amidoxime derivatives of general fonnula II
can be obtained in accordance with one of the following methods~
(1) By the reaction oE an a-halogeno-ester of the general formula:
Y - CH - COORl III
. . R
(wherein R and Rl are as hereinbefore defined, and Y
represents a halogen atom) with an amidoxime of the general formula: .

'

2.11L0~9 ~ N ~ OH
Ar - C~ IV
~2 wherein Ar is as hereinbefore defined. The reaction is genera]ly carried out in an aqueous organic solvent, such as a mixture of ethanol and ~ater or dimethylforrnamide and water, in the presence of an alkaline condensation agent, such as sodium hydroxide, potassium hydroxide or a tetraal];ylammonium hydroxide, and at a temperature between 20 and 80C. In certain cases, this reaction makes it possible to obtain directly the cyclised compound of general formula I without going through the intermediate compound of general formula II.
The amidoximes of general formula IV can be obtained by the action of hydroxylamine on a nitrile of the general formula:
1~ Ar - C~ V
wherein Ar is as hereinbefore defined. The reaction is generally carried out in an aqueous organic solvent, such as aqueous ethanol, at a temperature getween 20 and 80C.
(2) By the reaction of an ~-aminoxy-ester of the general formula-' , H2N - o - CE - COORl VI
~wherein R and Rl are as hereinbefore defined) or an acid 3Z1L~
.

addition salt, e.g. hydrochloride, thereof, with an imino-ether salt of the general formula:

Ar - C \ . HA VII
- C2~5 wherein Ar is as hereinbefore defined and HA represents a molecule of hydrogen chloride (HCl) or of fiuoboric acid (HBF~). The reaction is generally carried out in a basic oxganic solvent, such as pyr.idine, at a temperature between 15 and 35C.
The imino-ether salt of general formula VII can be obtained by the action of a solution of hydrogen chloride in ethanol on a nitrile of general formula V, or by the action of triethyloxonium fluoborate ~eerweinsalt) on an amide of the general formula:
Ar - CO~H2 VIII
.wherein Ar is as hereinbefore defined.

(3) By the reaction of a compound of the general formula:
R
- 0 ~ CH - COCl Ar - C~ IX
\ ~H2 HCl (wherein R and Ar are as hereinbefore defined) with an alcohol of the general formula: .
RlOH X

109210'.r3 wherein Rl is a~ hereinbefore defined. The reaction is carried out by heating the compounc1 of yeneral formula IX
in the presence of the alcohol of general formula X at a temperature between 50C and the boiling point of the alcohol.
According to another feature of the invention, the compounds of general formula I are prepared by the reaction of an a-amino~y-ester of general fonnula VI with I an imino-ether salt of general formula VII in a basic organic i 10 solvent, such as pyridine, at a temperature between 80 and 120C.
According to a still further feature of the invention, the co~pounds of general fonmula I are prepared by the process which comprises treating a compound of the general formula:

x I ~o~N XI

¦ wherein R and Ar are as hereinbefore defined and X represents a halogen (preferably chlorine or bromine) atom, with an alkali metal hydroxi*e in an aqueous solution at a temperature between 15 and 35C.
The compounds of general formula XI can be obtained by the action of an acid chloride of the general formula:
X - CH - CGCl R XII
.

3Z~

(wherein R and X are as hereinbe~ore defined) with an amidoxime of general formula IV.
The reaction is generally carried out in an organic solvent, such as dioxan or toluene, in the presence of pyridine.
The compounds of general formula-I obtained by the aforedescribed processes can optionally be purified by physico-chemical methods such as crystallisation or chromatography.
The 1,2,4-oxadiazin-5-one derivatives of the present invention exhibit remarkable properties which render th~m particularly useful in the agricultural field.
¦ The following Examples illustrate the preparationof 1,2,4-oxadiazin-5-one derivatives of general formula I
by processes hereinbefore described.
~XAMPLE 1 A mixture of ethyl 4-chlorobenzimidate hydrochloride (47.8 g), ethyl aminooxyacetate hydrochloride (34 g) and anhydrolls pyridine (~20 cc) is heated at the boiling p~int, ~0 whilst stirring, for 16 hours. The pyridine is then evaporated under reduced pressure (20 mmHg) and the concentrate is taken up with ethyl acetate (600 cc) and water (300 cc). The organic phase is decanted and then washed with water (3 x 100 cc). After drying over anhydrous sodium sulphate, the solvent is evaporated under reduced _ . . ,._ .. . .

~Z~L09 pressure (20 mm~Ig). The solid res:idue is taken up in diisopropyl ether (100 cc) and the crystals are filkexed off. 3-(4-Chlorophenyl)--5,6-dihydro-4H-1,2,4-oxadiazin-5-one (24.1 g) is thus obtained. After recrystallisation from ethanol (7 parts by volume), the p~oduct melts at Ethyl 4-chlorobenzimidate hydrochloride, used as starting material, can be prepared by the method of L. Weintraub, 5.R. Oles and N. Kalish, J. Org. Chem. 33, 7,679 (1963).

Following the procedure of Example 1, but starting with ethyl 2-chlorobenzimidate hydrochloride and ethyl aminoxyacetate hydrochloride, 3-(2-chlorophenyl)-5,6-dihydro~4H-1,2,4-oxadiazin-5-one, melting at 132C, is ¦ obtained in a yield of 80%.
Il By proceeding as described in Example 1 but using I appropriate starting materials of general formulae VI and I VII there were obtained the following products having the stated melting points aftex recrystallisation.

3-(4-Hydroxyphenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 251C (yicld 66%).

3-(4-Methoxyphenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 212C (yield 63%).

.

.

3-(2,4 Dichlorophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 179C (yield 58%).
EX~MPLE 6 3-[3~(Methy]thio)phenyl]-5,6-dihydro~4H-1,2,4-oxadiazin-5~one, m.p. 128C (yield 67%~.

0-Ethoxycarbonylmethyl-5-chlorothiophene-2-car~oxamidoxime (14.1 g) and dry sodium methoxide (2.9 g) in ethanol (140 cc3 are stirxed at ambient temperature for 3 hours. The ethanol is then evaporated under reduced pressure and the solid residue is taken up in distilled water (100 cc). The solution thus obtained is acidified by adding ~ hydrochloric acid t54 cc). The white crystals which are forned are filtered off and washed with water.
After drying, 3-(5-chlo~othien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one (10.7 g), melting at 210C, is ob-tained.
By proceeding as described in Example 7 but using appropriate starting materials of g~neral formula II, there were obtained the follo~ing products having the stated melting points.

3-(Thien-2-yl)-5,6-dihydro-4H-1,2,4~oxadiazin-5-~ne, m.p. 180C (yield 72%).

6-Methyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-f~

oxadiaz:;n-5-one, m.p. 187C (yield 87%).
EXAMPLE lO
, 3-(Thien-3-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 183C (yield 96%)-.
EY~MPLE 11 3-(Fur-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 186C (yield 77%).
EX~MPEE 12 3-(5-Methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 215C (yield 92%)~

3-tN-Methylpyrrol-2 yl) 5,6-dihydro-4H-1,2,4--oxadiazin-5-one, m.p. 143C (yield 69%).

3-(Pyrrol-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-S-one, m.p. 261C (yield 91%).

.
3-(3-Methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 100C (yield 89%).

3-(3-Bromothien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 127C (yield 89%)~

3-(4-Dimethylaminophenyl)-5,6-dihydro-4H-1,2,4~
oxadiazin-5-one, m.p. 210C (yield 81%).
, .. ~ _ .... . .

~2~

E~MPL3 18 3-(3-Nitrophenyl)-5,6-dihydro~4H-1,2,4-oxadiaæin-5-one, m.p. 210C (yield 90%).
EX~MPLE 19 3-(2-Iodophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 146C (yield 84%).

3-(3-Hydroxyphenyl)-5,6~dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 184C (yield 73%).

3-(3-Chlorophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one' m.p. 130C (yield 81%).

3-(4-Chloro-3-nitrophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 203C (yield 68%).
EX ~MPLE 2 3 3-(3-Fluorophenyl)-5,6-dihydro-4H-1,2 4-oxadiazin-5-one, m.p. 148C (yield 76%).

3-(2-Fluorophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m~p. 126C ~yield 71%).

3-(4-N,M-Dimethylsulphamoylp~enyl)-S,6-dihydro-4H-1,2,4-oxadiazin-5-one, m~p. l90~C (yield 81%).
~ .
~' ' ' .

~L0~;21()~3 3-(3~ -Dimethylsulphamoylpheny~)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 164C (yield 93%~.
~.XAMPLE 27 3-(3-Sulphamoylphenyl)-5,6-dihydro-4~I-1,2,4-oxadiazin-5-one, m.p. 205C (yield 64%).

3-[3-(Trifluoromethylthio)phenyl~-5,6-dlhydro-4H-1,2,4-oxadiazin-5-one, m.p. 132C (yield 76%).

I 3-(3-Methylsulphonylphenyl)-5,6-dihydro-4H-1,2,4-¦ oxadiazin~5-one, m.p. 203C (yield 97%).

3-(2 Bromophenyl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one, m.p. 123DC (yield 77%).
EXhMPLE 31 Chloroacetyl chloride (1.13 g) is added dropwise, ! over the course of 10 mlnutes, to a solution of thiophene-2-carboxamidoxime (1.42 g) in dioxan (20 cc). The white precipitate obtained is dissolved by adding pyridine (3 cc) to the reaction mixture. After 16 hours at a temperature of about 20C, a brown oil separates out. The solvents are evaporated at a temperature of about 20C under reduced pressure ~0 m~Ig followed by 1 mmHg), and the concentrate is then taken up in water ~10 cc). The precipitate obtained ~l0~JZ~ 3 is filtered off and washed with water (2 x 5 cc). After drying, 0-chloroacetyl-thiophene-2-carboxamidoxime (1.1 g), melting at 156C, is obtain~d.
0-Chloroacetyl-thiophene-2-carboxamidoxime (1 g) is d.issolved in toluene (20 cc) and the solution is heated under reflux for 16 hours. After decolourising with charcoal, the solution is concentrated under reduced pressure (20 m~Ig) and the crystals which are deposited are dried under reduced pressure ~1 ~Hg) at a temperature of about 20C. 5-Chloromethyl-3-(thien-2-yl)-1,2,4-oxadiazole (0.9 g), melting at 57C, is thus obtained.
5-Chloromethyl-3-(thien-2-yl)-1,2,4-oxadiazole (0.67 g) is dissolved in dimethylformamide (5 cc). A 2N
~ aqueous sodium hydroxide solution (5 cc) is added to the ¦ 15 solution obtained and the mixture is stirred for 30 minutes.
It is then acidified with 11~ hydrochloric acid (0~9 cc) and the crystals obtained are filtered off and washed with I water (4 x 10 cc). After drying, 3-tthien-2-yl)-5j6-dihydro-4~-1,2,4-oxadiazin-5-one (o.46 g), melting at 180C, is obtained.
- The following Examples illustrate the preparation of a 1,2,4-oxadiazolin-5-one derivative of general formllia I by the reaction of compounds of general formula III and IV
without separation of an intermediate amidoxime derivative ~5 of general fo,rmula TI which is formed and is cyclised ,, 2113~

immediately.

Thiophene~2-carbo~amidoxime (28.4 g) is added to a 2~ ethanolic sodium hydroxide solution (200 cc), and a solui-ion of ethyl bromobutyrate in ethanol (200 cc) is then added over the course of 30 minutes. The reaction mixture is stirred for 16 hours and the alcohol is then distilled at a temperature of about 25C under reduced pressure (20 m~g). The residue obtained is taken up in water (200 cc) and diethyl ether (100 cc). The organic phase is decanted and washed with water (100 cc). The aqueous liquors are combined and acidified with citric acid (14 g). A precipitate is obtained, which is filtered off and washed with water (3 x 20 cc) and then dried at a temperature of about 20C under reduced pressure (1 mmHg).
6-Ethyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one ~10.38 g), melting at 171C, is thus obtained. After recrystallisation from acetonitrile, the pure product melts at 176C.
~0 EXAMPLE 33 By following the procedure of Example 32 but starting with thiophene-2-carboxamidoxime (20 g) and ethyl bromophenylacetate (34.2 g), 6-phenyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one (10.3 g), melting at 173C after recrystallisation, is obtained.

Zl~!~

As mentioned heretofore the 1,2,4-oxadiazin-5-one derivatives of general formula I possess properties useful in the ~gricultural field.
When they axe use~ at doses of between 1 and 100 g/hl of water, they exhibit phytohormonal properties. In that case, they possess auxinic actions analogous to those of indolylacetic acid or of derivatives of the phenoxyacetic acidsD They are particularly useful in assisting the se~ting of fruit on certain plants (tomatoes), preventing the shedding of leaves or fruit, or increasing the formation of roots.
When they are used at rates of application of ~etween O.S and 10 kgjha, the 1,2,4-oxadiazin-5-one derivatives of the present invention exhibit herbicidal properties, in particular against dicotyledon plants, both in pre~ emergence and in post-emergence application.
For practical application the 1,2,4-oxadiazin-5-one derivatives of general formula I are rarely employed by themselves, but instead are generally employed in association with at least one carrier and/or a surface-active agent compatible with the active material and suitable for use in agricultural or horticultural compositions. In such compositions the content of active compound can be from 0.005 to 95% by weight according to the form of presentation.
The term "carrier" in the sense of the present ~z~

description denotes an organic or inorganic, natural or synthetic, material with which the active material is associated in order to facilitate its application to the plant, to seeds or to the soil, or to facilitate its S transportation, or its handling. The carrier can be solid (e.g. clays, natural or synthetic silicates, resins, waxes and solid fertilisers) or fluid ~e.g. water, alcohols, ketones, petroleum fractions, chlorinated hydrocarbons or liquefied gases).
The surface-active agent can be an emulsifying agent, a dispersing agent or wetting agent, which can be ionic or non-ionic, for example, salts of polyacrylic acids and of ligninsulphonic acids, and condensates of ethylene oxide with fatty alcohols, fatty acids or fatty amines, and especially products based on condensates of ethylene oxide such as the condensates of ethylene oxide with the octylphenol or nonylphenol.
The cornpositions can be prepared in the form of wettable powders, dusting powders, granules, solutions, suspensions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols.
The wettable powders are usually prepared in such a way that they contain from 20 to 95% by weight of active compound; they usually contain, in addition to a solid carrier, from 0 to 5% by weight of wetting agent, from 3 to , ~ ~ ., .
.. i ,~ .

10~3~

10% by weight of a dispersi.ny agent and, where necessary, from 0 to 10% by we.iyht of one ox more stabilisers and/or other adjuvants such as penetrating agents, adhesives or - anti-caking agents and dyestuffs.
~y way of example, the composition of a wettable powder is given below, the percelltages being expressed by weight 7 Compound of formula I 50%
calcium lignosulphate (deflocculating agent) 5%
isopropyl naphthalenesul~honate (wetting agent) 1%
silica anti-caking agent 5%
ll kaolin filler 39%.
'I . The powders for dusting are usually pr~pared in the form of a dust concentrate having a composition sirnilar to tbat of a wettable powder but without dispersing agent, 1. they can be diluted on site by means of a supplementary I amolmt of a solid carrier so that a composition which usually contains from 0.5 to 10% ~y weight of active compound is obtained.
- The emulsifiable concentrates which can be applied by spraying usually contain, in addition to the solvent and, where necessary, a co-solvent, from 10 to 50% (w/v) of active com~,ound, from 2 to 20% (w/v) of emulsifiers and from 0 to 20% (w/v) of appropriate additives, such as .. . -- 19 --. , .
.

__ _ ~Z~L0~3 stabilisers, penetrating agents, corrosion inhibitors, dyestuffs and adhesives.
The suspension concentrates, which can also be applied by spraying, are prepared in such a way that a stable fluid product which does not sediment is obtained.
They usually contain frorn 10 to 75% by weight of active compound, from 0.5 to 15% by weight of surface-active agents, from 0.1 to 10% by weight of anti-sedimentation agents such as protective colloids and thixotropic agents, from 0 to 10~/o by weight of appropriate additives, such as anti-foam agents, corrosion inhibitors, stabilisers, penetrating agents and adhesives and, as the carrier, water or an organic liquid in which the active material is substantially insoluble, certain organic solid materials or inorganic salts can be dissolved in the carrier to assist in preventing the sedimentation or to act as anti-freeze agents for the water.
Aqueous dispersions and emulsions, for example ~ompositions obtained by diluting a wettable powder or an emulsifiable concentrate as hereinbefore described with water, are also useful. These emulsions can be of the water-in-oil type or of the oil-in-water type and can have a thick consistency such as that of a "mayonnaise".
For a so-called "ultra-low volume" application, entailing spraying as very fine droplets, solutions in r~ .
}~ .

~1,9;~

organic solvents, which contain from 70 to 95% of active compound, are prepared n The compositions can contain other ingredients, for example protective colloids, adhesives or thickeners, thixotropic agents, stabllisers or sequestering agents, as well as other substances which are known to have pesticidal properties, in particular insecticides or fungicides.
A further example of an agricultural composition is given below.

A condensation product (10 parts~ of ethylene oxide and octylphenol, having 10 molecules of ethylene oxide per molecule of octylphenol, is added to a solution of 3- ( thien-2-yl)-5,6-dihydro-1,2,4-oxadiazin-5-one (25 parts) in a mixture (65 parts~ of equal parts of toluene and acetophenone. The solution is used for agricultural purposes, after dilution with water, at the rate of 100 cc of solution per 100 litres of water.
The phytohormonal activity of the 1,2,4-oxadiazin-5-one derivatives of the present invention is demonstrated in the following experiments.
(1) Settinq of fruit of tomatoes 1 drop (0.05 cc) of the solution or suspension of th~ compound to be studied is deposited on the ovary of ~, - ..
......

2~

emasculated flowers of tomato plants. After a perlod of I observation of 15 days, the percentage of fruit forrned 3 relative to the control is noted.
Used in this way, at a concentration of 100 mg/litre, , 5 the product of Example 8 shows a degree of setting of fruit of 100%, relative to the control (0%). The fruit formed i5 devoid of pips.
' , (2) Propaqation of tomato leaves ¦ , The 3rd and 4th leaves are taken from tomato stems (Marmande variety) having 5 to 6 l~aves. l~e petiole of , ' each leaf is di,pped, over a length of 2 to 3 cm, into the ¦ , ' solution to be studied, contained in a test tube. 8 Days , after startlng the experiment, the'number of roots fol^med ¦ on the petioles of the treated leaves is counted and their j 15 aspect is observed.
Used in this wayj at a concentration of 10 mg/litre, the product of Example 8 causes the formation of 100% of rooted leaves, whilst the formation is zero in the case of ' ' the petioles of control plants. In the same way, but at a' 20 concentration o* 1 mg/litre, the pro~ucts of Exarnples 9 and 11 ,cause the formation of 100% of rooted leaves~ With the ''product of Example 9 the roots are short and thick: with the product of Example 11 the roots are short,and thin.

, 1. ' ' , , .

~3~

The herbicidal activity of the comE)ounds of general formula I is demonstrated i.n the following,manner:
Seeds of various sp0cies, namely wheat (Triticum sativum), lentil (Lens culinaris), radish tRaphanus sativus), sugar beet (Beta vulqaris) and slender foxtail E~S~ aqrestis), are sown in plastic pot,s (180 cc capacity) containing to a height of 6 cm a mixture composed of 1/3 of clean earth, 1/3 of vegetable mould and 1/3 of river sand, at the rate of about 30 seeds psr pot. For each concentration of compound, two pots of wheat and four pots ll of the other species are used~
! For the purpose of a post-emergence treatment, the I sowing is carried out in a greenhouse one week before the I . start of the experiment so that the small plants are at the i 15 following stage at the time of treatmsnt:
¦ ' wheat and foxtail : 2 or 3 leaves lentil : 3 leaves beet and radish : 2 well-developed cotyledon leaves.
The treatment is carr,~ed out by spraying the solution or suspension of the product, the pots being placed on a pot-turner. Each pot is given 1 cc of the solution.
The doses of the product to be studied are 1, 8 and 10 kg/ha.
In pre-emergence testing, the seeded surface of the pots is ~llowed to dry, then covered to a depth of 1 cm with the same earth mixture: twice a day the pots are watered .

il 0~3Z10~3 by sprinkling. In post-emergence testing, the treated small plants are allowed to dry. rrhe earth mixture is moistened by placing the base of the pots in a tray containing water.
In both cases, the pots are kept in a greenhouse (22 to 24C, 70 to 8Q% relative humidity) under artificial light which provides 5,000 to 6,000 Lux at the level of the plants, for 17 consecutive hours per day.
Three weeks after the start of the treatment, the number of plants in each pot is counted, and their height is measured.
The results are expressed in percentages relative to the control plants.
¦ ~he results are summarised in the '~able which ! follows. The doses of active compound used are ln kg/hectare.
rrhe percentage destruction of treated plants is noted. In the Table the figure O indicates that the compound is inactive, the figure 100 indicates max~n~ activity.

.

.

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- - -. - - - - -~- 1- 1- 1- 1-' ~
rS~ ~n ~ I_ O ~ CO ~ '~

. ~h 1- ~ 1- - ----_ ~ ~ n t O 1-- O 1-- 01-- rx1 I-- Co I-- Co I-- r 1-- CO 1-- ~D ~- (D
. pJ l-h _ _ __ _ _ _ _ __ `. 00 00 00 00 00 oo oo Ulo (D .
_ _ _ _ It 1_ ~ 1- 1-1- 1- 1-1- 1- ~ ~
O C5~ O O O ~) O O O r~o O O O ~:) ~) rl ~d C~O 00 00 00 00 00 00 U10 1- L113 _ . _ W
.'. ' . O ~ ~1~> 0~ ~ 0~ ~ ~
Oo 00 O(n 00 00 00 00 00 ~ ~
. . .. b~ W
' . ~n u~ u~ ~ r~ ~ O ~ ~1 rD
I. . oo oo oo, oo oo oo oo oo .. .. . _ ~ l_ . __ _~
~ Vl r Ul ~ ~ O r ,~1 ~n. ~D Ul oo u~o 00 o~ oo ulo ulo oo ~
.... _ _- _ ~_ o o o o O o O o o o O o o o o O~
_ ~t U~ O Ul O ~) ~1 ~ Ul ~ O ~1 O ~ ~ O
00 00 00 UlO 00 00 00 O IJ- ~3 _ _ _ ~ k o ~9 . oo oo oo oo oo oo oo o ~ C~
_ _ . . _ W
1~ !~ (D
00 00 00 00 00 00 00 O ' 0 ~ ~ ~ . .
00 00 00 00 00 00 00 O pJ, .

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The present invention also includes within its scope a method of treating useful plants, lor example to assist the setting of fruit, to prevent the shedding of ; leaves or fruit or to increase the formation of roots, which comprises applying to the plant and/or its environment a composition compxising a 1,2,4-oxadiazin-5-one deri~ative of general formula I and a,carxier therefor and/or at least one surface active agent as hereinbefore described.
, A method for the control of weeds is also another ', , aspect of the present invention, said method comprising applying to the weeds, or to a locus in which weeds are growing or are expected to grow, a composition as mentioned above for treating useful plants.

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Claims (17)

The embodiments of the invention, in which an exclusive privilege or property is claimed, are defined as follows:

1. 1,2,4-Oxadiazin-5-one derivatives of the general formula:

wherein R represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, or a phenyl radical, and Ar represents a phenyl radical substituted by 1, 2 or 3 substituents. which - when two or three substituents are present - may be identical or different, selected from halogen atoms, the hydroxy radical, alkyl radicals containing 1 to 4 carbon atoms, alkoxy radicals containing 1 to 4 carbon atoms, alkylthio radicals containing 1 to 4 carbon atoms.
alkylsulphonyl radicals containing 1 to 4 carbon atoms, the trifluoromethylthio radical, the nitro radical, dialkylamino radicals containing 1 to 4 carbon atoms in each alkyl group, the sulphamoyl radical and dialkyl-sulphamoyl radicals containing 1 to 4 carbon atoms in each alkyl group, or Ar represents a thienyl. pyrrolyl or furyl radical unsubstituted or substituted by a halogen atom or an alkyl radical containing 1 to 4 carbon atoms.

2. 1,2,4-Oxadiazin-5-one derivatives according to claim 1 wherein R represents a hydrogen atom or a methyl or phenyl radical, and Ar represents the phenyl radical substituted by 1, 2 or 3 substituents selected from halogen atoms and methyl, hydroxy, methoxy, methylthio, methylsulphonyl, trifluoromethylthio, nitro, dimethylamino, sulphamoyl and dimethylsulphamoyl radicals, or Ar represents a thienyl, pyrrolyl or furyl radical unsubstituted or substituted by a halogen atom or the methyl radical.

3. 1,2,4-Oxadiazin-5-one derivatives according to claim 1 wherein Ar represents a thienyl radical optionally substituted by a halogen atom or an alkyl radical containing 1 to 4 carbon atoms.

4. 1,2,4-Oxadiazin-5-one derivatives according to claim 1, 2 or 3 wherein R represents a hydrogen atom or a methyl, ethyl or phenyl radical.

5. 3-(5-Chlorothien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

6. 3-(Thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

7. 6-Methyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

8. 3-(Thien-3-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

9. 3-(5-Methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

10. 3-(3-Methylthien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

11. 3-(3 Bromothien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

12. 6-Ethyl-3-(thien-2-yl-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

13. 6-Phenyl-3-(thien-2-yl)-5,6-dihydro-4H-1,2,4-oxadiazin-5-one.

14. A process for the preparation of a 1,2,4-oxadiazin-5-one derivative as claimed in claim 1 which comprises (A) cyclising an amidoxime derivative of the general formula:

(wherein R and Ar are as defined in claim 1. and R1 represents an alkyl radical containing 1 to 4 carbon atoms) by heating in a basic medium at a temperature between 20° and 70°C., or (B) reacting an .alpha.-halogeno-ester of the general formula:

(wherein R is as defined in claim 1, R1 is as defined above and Y represents a halogen atom) with an amidoxime of the general formula:

(wherein Ar is as defined in claim 1) in an aqueous organic solvent medium in the presence of an alkaline condensation agent at a temperature between 20° and 80°C., or (C) reacting an .alpha.-aminoxy-ester of the general formula:

(wherein R is as defined in claim 1 and R1 is as defined above), or an acid addition salt thereof, with an imino-ether salt of the general formula:

(wherein Ar is as defined in claim 1 and HA represents a molecule of hydrogen chloride or of fluoboric acid) in a basic organic solvent at a temperature between 80°
and 120°C., or (D) treating a compound of the general formula:

(wherein R and Ar are as defined in claim 1, and X
represents a halogen atom) with an alkali metal hydroxide in aqueous solution at a temperature between 15° and 35°C.

15. A method for the phytohormonal treatment of useful plants which comprises applying to a useful plant and/or its environment a phytohormonal quantity of at least one 1,2,4-oxadiazin-5-one derivative as claimed in claim 1.

16. A method for the control of weeds which comprises applying to the weeds, or to a locus in which weeds are growing or are expected to grow, a herbicidal quantity of at least one 1,2,4-oxadiazin-5-one derivative as claimed in claim 1.

17. A method according to claim 16 in which the rate of application of oxadiazinone derivative to a weed-infested locus is 0.5 to 10 kg per hectare.