CA1077038A - Herbicidal 4-oxy-pyrimidine derivatives - Google Patents

Abstract

ABSTRACT
Herbicidal pyrimidine compounds of the formula:-

Description

107~038 This invention relates to herbicidal processes and compositions utilising pyrimidine compounds as active ingredients, and to certain novel pyrimidine compounds.
According to the present invention there is provided a process of inhibiting the growth of ~mwanted plants, which comprises applying to the plants, or to the growth medium thereof, a herbicidally effective amount of a pyrimidine compound of formula (I), Rl~ OR 3 N ~ N
R
(I) or an acid addition salt thPreof, wherein R represents (a) a hydrogen atom; (b) a phenyl radical optionally substituted by one or more alkyl, alkoxy, fluorine, chlorine, or bromine atoms; or (c) an alkyl or alkenyl radical optionally substituted by one or more of the following:
a fluorine, chlorine, or bromine atom;
a cycloalkyl, hydroxy, alkylthio, furyl, pyridyl or mono-or di-alkylamino radical;
a phenyl radical optionally substituted by one or more alkyl, fluorine, chlorine, hromine, phenyl, cyano, haloalkyl, or alkoxy radicals;
or an alkoxy radical optionally substituted by one or more . 2 .. . ... .

- : ' , , ~ .
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~077038 phenyl or alkoxy radicals;
Rl represents a lower alkyl radical;
R represents a hydrogen atom or a lower alkyl radical;
and R3 represents an alkyl or alkenyl radical optionally substituted by one or more of the following:
cycloalkyl; pyridyl; naphthyl; or phenyl optionally substituted by one or more fluorine, chlorine, bromine, iodine, haloalkyl, cyano, alkyl, hydroxymethyl, or 4-methyl-

2-propyl-6-pyrimidin-yloxymethyl radicals.
When R is a phenyl radical substituted by an alkyl or alkoxy radical, the alkyl or alkoxy radicals may each have, for example, from 1 to 4 carbon atoms. When R is an alkyl radical, it may contain, for example, from 1 to 12 or more carbon atoms. Preferably, when R is an alkyl radical it contains from 1 to 6 carbon atoms; it may be, for example, a methyl, ethyl, propyl, _ propyl, butyl, isobutyl, amyl, or hexyl radical.
When R is an alkyl radical substituted by a cycloalkyl, alkylthio, monoalkylamino, or dialkylamino radical, the cycloalkyl radical may contain for example from 3 to 6 carbon atoms; the alkylthio radical from 1 to 6 carbon atoms; and the one or two alkyl groups in the mono- and dialkylamino radicals may each contain, for example, from 1 to 6 carbon atoms. When R is a phenyl radical substituted by an alkyl, alkoxy, or haloalkyl group, each of these groups ~07703~

may contain, for example, from 1 to 4 carbon atoms. The haloalkyl group may be for example a trifluoromethyl group.
When R is an alkyl radical substituted by an alkoxy radical which is itself substituted by an alkoxy radical, each alkoxy radical may have for example from 1 to 6 carbon atoms. When R is an alkenyl radical it may for example contain up to six or more carbon atoms. Particular examples of alkenyl radicals within this range include allyl and crotyl radicals. Examples of substituted alkenyl radicals include the alpha-trifluorinated propenyl radical (CF3CH=CH-), the styryl (i.e. phenylvinyl) radical (PhCH=CH-) and the furylvinyl radical.
Preferably the lower alkyl radical Rl has not more than three carbon atoms. More preferably Rl is a methyl group.
When R2 is a lower alkyl radical, it preferably has no more than four carbon atoms.
The group R3 may contain for example up to eight or more carbon atoms. Examples of alkyl radicals falling within this range include ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, 2-methylbutyl, and 2-ethylbutyl. A
preferred alkyl radical is lsobutyl. Examples of alkenyl radicals include allyl and crotyl radicals.
When R3 is an alkyl radical substituted by a cycloalkyl radical, the cycloalkyl radical may have for example from : :.
-. .. . :
:
.
-: .

1077()38

3 to 6 carbon atoms. R3 may be, for example, a cyclohexyl-methyl radical. When R3 is an alkyl radical substituted by an alkyl- or haloalkyl- substituted phenyl radical, the alkyl or haloalkyl substituent may contain from 1 to 4 carbon atoms. R3 may be, for example, a benzyl radical, the phenyl ring of which may optionally be substituted by one or more fluorine, chlorine, bromine, iodine, haloalkyl, or cyano radicals.
Sub-groups of compounds falling within the broad class of compounds useful in the process of the invention include those in which R is a propyl or allyl radical, Rl is a methyl group, R2 is a hydrogen atom and R3 is a cyclohexylmethyl group or a benzyl group optionally substituted as set forth above. A further sub-group comprises those compounds in which ~ is a benzyl radical, optionally substituted as set forth above, Rl is a methyl group, R2 is a hydrogen atom, and R is a propyl, iso-butyl, or butyl radical.
The identity of the acid which is used to form the acid addition salts of the compounds of the invention is not critical and a wide variety of acid addition salts of any particular compound may therefore be used. For reasons of convenience and economy, however, salts derived from the readily available mineral acids are preferred, although others may be used ir desired. In considering the choice of acid, the purpose for which the salt is to be used will , ~(~7~7038 be taken into account; salts formed from herbicidal acids which are highly persistent in soil would obviously not be suitable for applications in which crops are to be ~ planted shortly after the herbicide is applied. Particular S examples of acids which may be used to form the acid addition salts include hydrochloric, hydrobromic, sulphuric, nitric, and phosphoric acids.
Particular examples of compounds useful in the invention are listed in Table I below, together with a characterising physical constant.

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1077038 .

The compounds used in the invention are herbicides phytotoxic towards a range of grass species and dicotyle-donous species. They are generally more effective by pre-emergence application than by post-emergence application.
S That is to say, they are generally more effective when applied to soil to prevent the growth of plants from seed or seedlings present in the soil than they are when applied to the above-ground parts of growing plants. The rate at which the compounds are applied will depend upon a variety of factors, such as for example the particular compound chosen for use and the identity of the plants whose growth is to be inhibited. As a general guide, however, an application rate within the range from 1 to 10 kilograms inclusive per hectare is usually suitable.
The compounds of the invention have been found to be severely phytotoxic to grass weeds and certain dicotyledonous weeds at rates of application which do not substantially damage certain crop plants, notably soya bean, ground nut, cotton, wheat, barley, and rice. In a further aspect, therefore, the invention provides a process of selectively inhibiting the growth of weeds in crops of soya bean, ground nut, cotton, wheat, barley, and rice, which comprises applying to the crop area, before the crop emerges, a compound of formula (I) or an acid addition salt thereof, as hereinbefore defined, in an amount sufficient to inhibit the - ~ .,, , , .. .. .
-.~, .
~ . ...

` ~077038 growth of the weeds but insufficient substantially to damage the crop plants.
The rate at which the compound is applied will depend upon the identity of the crop and upon the particular compound chosen for use, but in general an amount of from 1 to 4 kilograms per hectare will be suitable.
The compounds used in the process of the invention are preferably applied in the form of a composition, in which the active ingredient is mixed with a diluent or carrier.
In another aspect, therefore, the invention provides a herbicidal composition, comprising as an active ingredient a pyrimidine compound of the formula:-R2 ~,~oR3 N ~ N

wherein R, Rl, R2 and R3 are as hereinbefore defined, in admixture with a solid diluent or a liquid diluent containing a surface-active agent.
The solid compositions of the invention may be for example, in the form of dusting powders, or may take the form of granules. Suitable solid diluents include, for example, kaolin, bentonite, kieselguhr, dolomite, calcium, carbonate, talc, powdered magnesia, and Fuller's earth.

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Solid compositions may also be in the form of disper-sible powders or grains comprising in addition to the active ingredient, a wetting agent to facilitate the dispersion of the powder or grains in liquids. Such powders or grains may include fillers, suspending agents and the li~e.
Liquid compositions include aqueous solutions, dispersions and emulsions containing the active ingredient preferably in the presence of one or more surface active agents. Water or organic liquids may be used to prepare solutions, dispersions, or emulsions of the active ingredient. The liquid composi-tions of the invention may also contain one or more corrosion inhibitors for example lauryl isoquinolinium bromide.
Surface active agents may be of the cationic, anionic or non-ionic type. Suitable agents of the cationic type include for example quaternary ammonium compounds, for example cetyltrimethyl ammonium bromide. Suitable agents of the anionic type include for example soaps, salts of aliphatic mono-esters of sulphuric acid, for example sodium lauryl sulphate; and salts of sulphonated aromatic compounds, for example dodecylbenzenesulphonate, sodium, calcium and ammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl- and triisopropyl-naphthalenesulphonic acid. Suitable agents of the non-ionic type include, for example, the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and ... . .:
' . : . -: ~
:. .,:
.: :
~: , cetyl alcohol, or with alkyl phenols such as octyl-phenol, nonylphenol, and octylcresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitol monolaurate; the condensation products of the said partial esters with ethylene oxide and the lecithins.
The compositions which are to be used in the form of aqueous solutions, dispersions or emulsions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient, the concentrate being diluted with water before use. These concentrates are usually required to withstand storage for prolonged periods and after such storage to be capable of dilution with water in order to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. In general concentrates may conveniently contain from 10 to 85% and preferably from 25 to 60% by weight of active ingredient. Dilute preparations ready for use may contain varying amounts of the active ingredient, depending upon the purpose for which they are to be used; however, dilute preparations suitable for many uses contain between 0.01% and 10.0% and preferably between 0.1%
and 1% by weight of the active ingredient.
In a further aspect the invention provides novel pyrimidine compounds having herbicidal properties, having .""' ~ i . . ~. .
'- : `, the formula (I):

R ~ OR
N ~ N
R
(I) and acid addltion salts thereof, wherein R represents (a) a hydrogen atom, (b) a phenyl radical optionally substituted by one or more alkyl, alkoxy, fluorine, chlorine, or bromine atoms; or (c) an alkyl or alkenyl radical optionally substituted by one or more of the following:-a fluorine, chlorine, or bromine atom;
a cycloalkyl, hydroxy, alkylthio, furyl, pyridyl, or mono-or di-alkylamino radical; a phenyl radical optionally substituted by one or more alkyl, fluorine, chlorine, bromine, phenyl, cyano, haloalkyl, or alkoxy radicals;
or an alkoxy radical optionally substituted by one or more phenyl or alkoxy radicals:
Rl represents a lower alkyl radical;
R2 represents a hydrogen atom or a lower alkyl radical;
and R3 represents an alkyl or alkenyl radical optionally substituted by one or more of the following:
cycloalkyl; pyridyl; naphthyl; or phenyl optionally substituted by one or more fluorine, chlorine, bromine, Lodine, haloalkyl, cyano, alkyl, hydroxymethyl, or 4-, . . .: .: ~, . .: . : - - -;

.. : . ~ .: -107703~

methyl-2-propyl-6-pyrimidinyloxymethyl radicals; provided that when R is hydrogen or methyl, R3 is not an alkyl radical of 1 to 4 carbon atoms or a benzyl radical.
The compounds used in the invention may be prepared by processes which are known in themselves. Thus they may be prepared by the procedure shown in Scheme A below:-Scheme A

RlCCHCoR4 + NH NH2 Rl ~ O
Il ¦l ~ / N~,NH
O O C T
I R
R (I) (II) Rl ~ C1 (II) + POC13 N ~ N

R2 (III) Rl l~OR3 (III) + R30M - > I 1¦
R

(IV) In Scheme A, the symbols R, Rl, R2, and R3 have any of the meanings previously assigned to them. R4 stands for a hydrocarbyl group, preferably a lower alkyl group, for example an alkyl group of 1 to 4 carbon atoms. M stands for .
- ~ ~ ,. ....
: . .. . :

~)77038 an alkali metal, for example sod:ium or potassium. In Scheme A, an acyl-acetic ester RCCH2COR is reacted with a amidine O O
derivative (I). The amidine derivative is normally obtained as an acid addition salt, for example, the hydrochloride.
For reaction with the acylacetic ester, the amidine base is liberated from its acid addition salt by mixing a solution of the latter with an equimolar proportion of a base, for example sodium ethoxide. The reaction between the acyl-acetic ester and the amidine is preferably carried out in a solvent. Preferred solvents include lower alcohols, for example methanol and ethanol. The pyrimidine derivative (II) obtained from the reaction of the acylacetic ester and the amidine may then be converted to the 4-chloro-pyrimidine (III) by treatment with phosphorus oxychloride. Conveniently, the pyrimidine derivative (II) is heated under reflux in an excess of phosphorus oxychloride. The 4-chloro- compound so obtained may be isolated by conventional methods, for example by distilling off the excess of phosphorus oxy-chloride, and adding ice, followed by purifying the remaining pyrimidine (III) by recrystallisation from an appropriate solvent or distillation. The 4-chloropyrimidine may then be converted to the 4-substituted derivative (IV) by reacting it with an alkali metal derivative of an alcohol, R30M.

, . .,. :. .
- . . . ..
... : . - :
- - :, .. . . .
- . : - - -The reaction is conveniently carried out in a solvent for the reactants. The solvent may comprise, for example, the alcohol R30H from which the metal derivative R30M is prepared. The metal used to prepare the derivative R30M
will be an alkali metal or an alkaline earth metal, for example sodium, potassium, calcium, or magnesium. Where the solvent to be used comprises the alcohol R30H, the prepar-ation of the 4-substituted derivative (IV) may conveniently be carried out by dissolving the metal, for example sodium, in an amount which is at least equimolar with respect to the amount of the 4-chloropyrimidine derivative to be used, in an excess of the alcohol R30H, then adding the 4-chloro-pyrimidine derivative, and heating the reaction mixture for sufficient time to bring about completion of ~he reaction.
lS The temperature of the reaction is not critical but by way of general guidance, temperatures in the range from 25 to 100C are generally suitable while from 60 to 100C is generally preferred. The 4-substituted pyrimidine may be isolated from the reaction mixture by conventional methods, for example by pouring the mixture into water, extrdcting the aqueous mixture with an organic solvent, and evaporating the organic solvent to recover the extracted material. The latter may then be distilled or recrystallised by conventional methods.

, . . .
.

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107703~

Where it is preferred not to use an excess of the alcohol R30H as the solvent for the preparation of the 4-substituted derivatives (IV), the reaction may be carried out in an aprotic solvent for example a hydrocarbon solvent, for example toluene or light petroleum. Other solvents include for example dipolar aprotic solvents, for example dimethyl sulphoxide, and ethers, for example dioxan.
The following Examples illustrate the invention.

This Example illustrates the preparation of Compound no 15 of Table I.

4-Chloro-2,6-dimethylpyrimidine (4.28 g) was added to a solution of sodium (0.92 g) in isobutanol. The mixture was heated under reflux for 30 minutes, concentrated, and water added to the residue. The mixture was extracted with chloroform and the extracts dried and evaporated. The pale yellow oil was distilled at an oven temperature of 90C and a pressure of 0.1 Torr to yield a clear, colourless mobile oil having a refractive index n25 = 1.4757, identified as compound no 15 of Table I.
Most of the compounds listed in Table I were prepared by the procedure described above for compound no 15, that is to say by reaction of the appropriately substituted .. . . . .
; . . . ~
-, , . ... : , .

4-chloropyrimidine with a metal derivative of the appropriate hydroxy compound R30H. The bulk of the substituted 4-chloropyrimidines required as intermediates are known compounds.
Physical constants are tabulated below for those 4-chloro-pyrimidine derivatives which appear to be new:-Rl~

N ~ N
R

(III) :: : ....

-.
, .. ~:
;

~077038 _ ~E~ U
~ ~ ~, ~, o E~ O O C~ O C~
u~ ~ ~ o u- o o o a~ o o ~ o Z o ~ r ~ O ~9 _I O
O ~
I u~ I i~ I I I u~ I I n I
X o I 9 ~O o . a~
O ~1 ~ O
~; _, ~, I~ 1~
~ . . . . ~ . . ,, .
H P~ l C~
u~ Ql Ql Ql ~:
:~ ~ c ~
~ C
.
HH c~ m :: m m m m m m m m m m ~¢ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
E~ _, m m m m m m m m 3: m m m . P~ ~
. ~ Z
y C~
~ 1~ >1 N ~~ r 1: ~ N N N 1: N ~ ` I
a~ N,~: ~ ~ ~\
~ m o P~ ~1 r4 Q ~ ~ ~ O I m o O; O X ~1 0 ~ X ~ Q m ~o u --/
o ~ s o c~ 1 ' ) I m m m o U C~ C~ 11 11 U ~ ~c U ~4 ,C~ ~C., ~ I 1I m 5:
I I I I I I I ~ ~ ~ e~
_ Y

~ , : ... .. : .

.. ` .:. :. :: : : - . . . ~, . : . .; - - . :. . -:. . . . .. ~ ~
. ,, , . ~ :
. , ~ i . .. .: ... .

107703~

~ , ~
Z I
U ~ ~ U~
~ ~ ,, ~~ _, ,, ~
c ~C ~i~a ~c H ~`I
O ~
H ~'7 ~ r~7 ') H _I
E~1~ ~ C ) l ~

y tr: o ~
11 ~ ~ r~
~ ~ ~ o I I I ~

` ' ' ' ., .:
, . .
~, ..
.~
.

~ 107~7038 The above 4-chloropyrimidines were prepared by heating the corresponding 4-pyrimidones (II) with phosphorus oxychloride according to standard procedures. Physical constants are tabulated below for those 4-pyrimidone derivatives which appear to be new.

Rl~
N ~ N
R

(II) : :. . .. ., ... ~., :
, - .. : . . .~, : . i , ., : , .. ~........ . . . .
:- . ;

J. 1077038 _ o E~ u~ LO
H ~ ~1 ~ ~ D
O ~ o ~ x ~D ~`I
P~ _I o~ ~ ~1 ~ _I _I ~1 I I I I ~1 1 1 1 1 ~ I ~
~ co u~ I O
Z ~
H ~ I ~ er O
E~ r~ ~ Ln .
_ ....... __ H ~I
HH ~ ~ ~ C
Ii3 . . _ a _l $ 3 ~ ~

~ Z
O
:>~ ~ N ~ I el' I
^ N N N ~ N ~ ` ~r N
~~I rC
C~ ~ R ~ .4 a) I 5: 5:
-- 5~ ~ ~1 0 --I X ~1 ~ ~ ~ ~O
O ~ U ~ . ...
O ~ O ~ .C ~ 11 1 1 ....
t~ I I ~ _I ~ ~ ~ E4 5 ~ ~

5~ ~ S ~ ~ O
_ ~ ' ' '' , ' ~ , '' ~ ' '' ' '' . ' ' ' , ~ I

~077038 oC~
H
O
Pl t'~
t~ O
Z
H ~ O ~1 E~ _~ ~

a H ~`J~ ~ ~ ~ 3 z O
C~
1.1 _ C~ :S

~1 ~
~ ~ r~
~ ~ ,Y ~
O C) ~ ) ~ O
, ~ .
Y Y r ~ 33 ~

:: , :- ~
: ' 1 ' ,: , .: . , ; .: .

: :. : . .: ` -- .; ;~ , : - .

A small number of the compounds in Table I were prepared using procedures which are additional to those described for Scheme A above. The preparation of these compounds and of some intermediates is described below.

Compound no. 115 A mixture of 2-benzyl-4-isobutoxy-5-benzylpy~imidine (Compound 102 of Table I) (5.0 g) and N-bromosuccinimide (3.48 g) in dry chloroform (15 ml) was refluxed ror 5 hours, cooled, and diluted wi~h more chloroform. The diluted reaction mixture was washed with dilute sodium carbonate solution, then with water, dried, and evaporated. The residual orange-red oil was distilled at an oven temperature of 158-160C and 0.05 Torr to give a colourless viscous oil, which slowly solidified (m.p. 43-45C).

Compound no. 116 Propylamine (5 ml) was added to a solution of compound no. 115 (1.43 g) in acetonitrile (15 ml). The solution was warmed to 60C for 2.5 hours, cooled and poured into water.
The product was extracted with chloroform and the extract washed with brine, dried, and evaporated to leave a yellow oil. Distillation at an oven temperature of 140-145C and a pressure of 0.15 Torr gave compound 116.

" ': -, .

, ~ , ~077038 Preparation of 6-methyl-2-styryl-4-pyrimidone 2,3-Dimethyl-6-hydroxypyrimidine (30 g) and benzaldehyde (25.65 g) in acetic anhydride (70 ml) were heated at 150C
for 8 hours. The mixture was concentrated, cooled, and stirred with dilute aqueous sodium bicarbonate solution.
The precipitated solid was collected, washed, dried, and recrystallised from chloroform/petroleum (b.p. 30-40C) to give the required 6-methyl-2-styryl-4-pyrimidone. This was converted into the corresponding 4-chloro compound in the usual way with phosphorus oxychloride which was then used as an intermediate for compounds 117 and 118.

Preparation of 6-methYl-4(2-methylbutoxy)-2-2(4-cyanophenyl) ethylpyrimidine (Compound no. 96) 2-(4-Cyanostyryl)-6-methyl-4-(2-methylbutoxy)-pyrimidine (1.87 g) and p-toluenesulphonyl hydrazide (2.28 g) were heated under reflux in 2-methoxyethanol (25 ml) containing ethanolamine (0.19 g) for 2 hours. The mixture was cooled, poured into water, and extracted with dichloromethane. The extracts were washed with brine, dried, and evaporated. The remaining oil was purified by passage through a silica gel column in dichloromethane. Evaporation of the dichloro-methane solution gave the product (compound no. 96) as an oil.

-.
: :
. : . .
::, ; / I` ~ ' , .. :: . . , , ~-..
: ~ . . : , : :
-:. : . .

~07703~

Preparation of 2-(3!3,3-trlfluoropropenyl)-6-methyl-4-pyrimidone A mixture of 2,4-dimethyl-6-hydroxypyrimidine (22.02 g), trifluoroacetaldehyde hydrate (20.6 g) and acetic anhydride (90 ml) was stirred at 150C for 13 hours. Moxt of the excess of acetic anhydride was removed lmder reduced pressure and the cooled residue stirred with dilute sodium bicarbonate solution. The solid which separated was collected, dried, and washed with ether and then with petroleum to give the white crystalline product. This was converted into the corresponding 4-chloropyrimidine and then into compounds 91 and 92 by the method described in Scheme A.

Preparation of 2-(3 t 3,3-trifluoroPropYl)-6-methyl-4-pyrimidone A solution of 2(3,3,3-trifluoropropenyl)-6-methyl-4-pyrimidone (5 g), prepared as described above, in ethanol (80 ml) was shaken in a hydrogen atmosphere with a 5%
palladium on charcoal catalyst (0.2 g) until the calculated amount of hydrogen was absorbed. The catalyst was removed and the filtrate evaporated to give the product, having a melting point of 172-173C. This was converted into the corresponding 4-chloropyrimidine and then into compound no.
90 by the method described in Scheme A.

This Example illustrates the preparation of 4-benzyloxy-2-~-chlorobenzyl-6-methylpyrimidine (Compound no. 108 of Table 1).
(a) Preparation of 4-chlorophenylacetamidine.
Dry hydrogen chloride was passed through a mixture of 4-chlorobenzyl cyanide (50 g), ethanol (25.1 g) and cyclo-hexane (45 ml) maintained at 20-30C until saturated (3 hours).
Dry air was then passed through the mixture for 1 hour to remove excess of hydrogen chloride. This mixture was added slowly to isopropanol (250 ml) saturated with ammonia and maintained at 20-30C. When the addition was complete more ammonia was passed in to saturation. The mixture was then left at room temperature overnight. The ammonium chloride was filtered off, and the filtrate evaporated to dryness.
The residue was washed with ice-cold acetone to give 4-chlorophenylacetamidine hydrochloride, m.p. 184C.
(b) Preparation of 2-p-chlorobenzyl-6-methylpyrimid-4-one.
The amidine hydrochloride from (a) above (50.0 g) was added to a solution of sodium (12.35 g) in ethanol (300 ml) followed by ethyl acetoacetate (34.89 g). The mixture was stirred at room temperature overnight and then heated under reflux for 2% hours. The mixture was concentrated to a small volume and the residue dissolved in water, cooled, and ;, , : .: . . . : :
:: .. : . .. ..
. : ~: .... : . ,: . -: . . . ., . . .: ,,: .

.~
.... .

1(~77038 brought to pH 5-6 with acetic acid. The precipitated solid was washed with acetone and dried, giving the pyrimidone, with a melting point of 212-215C.
(c) Preparation of 4-chloro-2-~-chlorobenzyl-6-methyl pyrimidine.
A mixture of the pyrimidone from ~b) above (37.04 g) and phosphorus oxychloride (130 ml) was heated under reflux for 1 hour. The mixture was concentrated to a small volume and the residue cooled and added carefully to ice and water.
The mixture was made alkaline with concentrated ammonia.
The product was extracted with chloroform and the extracts washed with brine and dried. The extracts yielded a crude product which was dissolved in a mixture of ether and petroleum (b.p. 30-40C). The solution was filtered and the filtrate evaporated to yield the 4-chloropyrimidine, with a melting point of 70-71.5C.
(d) Preparation of 4-benzyloxy-2-~-chloroben~yl-6-methyl-pyrimidine.
Benzyl alcohol (2.03 g) was added to a suspension of sodium hydride (0.522 g) in acetonitrile (25 ml). After cessation of hydrogen evolution, the chloropyrimidine (5.0 g) from (c) was added The mixture was stirred at room temperature overnight and poured into water. The product was extracted with chloroform and the extract washed with brine, dried, and concentrated to an oil. Distillation at 176-180C, 0.15 Torr gave the product as a pale yellow oil, with a refractive index nD 1.5876.

This Example ill~lstrates the herbicidal properties of compounds used in the process of the invention. Each compound (0.12g) was formulated for test by mixing it with 5 ml of an emulsion prepared by diluting 100 ml of a solution containing 21.8 grams per litre of Span 80 and 78.2 grams per litre of Tween 20 in methyl cyclohexanone to 500 ml with water. Span 80 is a Trade Mark for a surface-active agent comprising sorbitan monolaurate. Tween 20 is a Trade Mark for a surface-active agent comprising a condensate of twenty molar proportions of ethylene oxide with sorbitan mono-oleate. The mixture of the compound and the emulsion was shaken with glass beads and diluted to 12 ml with water.
The spray composition so prepared was sprayed on to young pot plants (post-emergence test) of the species named in Table II below, at a rate equivalent to 1000 litres per hectare (lO kilograms of pyrimidine compound per hectare).
Damage to plants was assessed 14 days after spraying by comparison with untreated plants, on a scale of 0 to 3 where 0 is no effect to 25% damage and 3 represents 75 to 100%
kill. In a test for pre-emergence herbicidal activity, .-. .

- . . .:

~07703~

seeds of the test species were placed on the surface of fibre trays of soil and were sprayed with the compositions at the rate of 1000 litres per hectare. The seeds were then covered with further soil. Fourteen days after spraying, the seedlings in the sprayed fibre trays were compared with the seedlings in unsprayed control tray~s, the damage being assessed on the same scale of O to 3. The results are given in Table II below:-.
. .~ . .

.

~077038 TABLE IV

*PRE- OR POST- TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATION Lt To Wo/O Ll Cn St .
l B - 1 O

A O O - O O 3 .

A 1 2 O ~ O O 3 A 3 1 O l O 3 B O O O O O O

6 B O O O O O O

7 B O O O O O O

8 B 3 3 2 2 O

9 B 1 2 O O O -O O O O O

.

. -: . .
.. .
.: . .~

107703~
TABLE IV CONTINUED...

~.
PRE- OR POST-TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATIONLt To Wo/O Ll Cn St A O O O O O O

A O O - O O O

A O O O O O O

. OO OOOO

107703~

TABLE IV CONTINUED...

PRE- OR POST-TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATIONLt To Wo/O Ll Cn St 37 B _ _ _ _ _ _ B O O O O O O

TABLE IV CONTINUED...

PRE- OR POST- TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATION Lt To Wo/O Ll Cn St .

A O O O O O
66 B _ o -~0770'~

TABLE IV CONTINUED...

PRE- OR POST-TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATIONLt To Wo/O Ll Cn St . A 1 2 0 1 0 3 ; 1 1 1 2 0 3 . .

~077038 TABLE IV CONTINUED...

. PRE- OR POST- TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATION Lt To ~o/O Ll Cn St B O O O O O O
A 2 O O O o . A 3 O O O O O

. 3 O O O O 2 A O~ 1 O O O 1 . A O 2 O 2 O 2 . 2 2 13 G 3 , , ' . ' ' :
: .

1077~)38 TABLE IV CONTINUED...

PRE- OR POST-TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATIONLt To '~o/O Ll Cn St B O O O O O O
A O 1 0 0 o - , :. , TABLE IV CONTINUED...

PRE- OR POST-TEST PLANTS
COMPOUND EMERGENCE
NO APPLICATIONLt To Wo/O Ll Cn St llO B 3 3 1 2 O

A 3 3 l 3 1 3 113 r 3 3 3 3 O 2 . A 1 2 O 2 1 3 * In the table, B means pre-emergence application and A means post-emergence application.

.- ,. , "" .. ..... . . . ...

:, , ~077~)3&~

The names of the test plants were as follows:-Lt Lettuce To Tomato W0/0 Wild oats and cultivated oats~ Wild oats (Avena fatua) are used in the post-emergence test and cultivated oats in the pre-emergence test.
Ll Lolium perenne (perennial rye grass) Cn Cyperus rotundus St Setaria viridis This Example illustrates the herbicidal properties of compounds used in the invention. Each compound was formulated for test by mixing an appropriate amount with 5 ml of an emulsion prepared by diluting 160 ml of a solution containing 21.8 g per litre of Span 80 and 78.2 g per litre of Tween 20 in methylcyclohexanone to 500 ml with water. The 5 ml of emulsion containing the test compound was then dlluted to 40 ml with water and sprayed on to the range of test plants named in Table V.
A pre-emergence test was also carried out as described in Example 3. The plants were observed for 2 weeks after treatment in the post-emergence test and for 3 weeks in the pre-emergence test. Damage to plants was assessed on a scale of 0 to 5 where 0 is 0 to 20% damage and 5 is complete kill. The results are given in Table V below:-:~: , :

10770;~8 _ ~ o o o o o o I o o o o ~ o o o o o ~ o o o ~ o O O ~r er O O O ~r O
o u~ o ,, er ~ ~r I u~ u~ O
u~ ~1 n O O ~ Lr~ _~ ~1 ~ u~ O
~ I ~1 O O ~ ~ 0~ U~ n~
a ~1 n o o O O ~1 O O ~r ~r ~ ~1 er ~ I o l l ~ l I o l I o u~ ~ O ~r O O ~ ~r ~ O u~ n o ~ X oo o o o o o o o o o ~ ~ O ~ ~ O ~ u~ ~ _l n u~ ,~
E~ O ~ ~ ~1 ~ O ~7 O -I ~ ~ ~
E~ P~ O O O O O O O O l O -I
~ 0 ~1 _I . O N ~ O ~`1 n 1~7 ~
H O _I _I O t~l O ~ _I O ~r O
~ 00 O O O ~ 00 U') 00 ~ O O O O u7 ~r -I O ~'1 ~ O

N O _i ~ O ~ ~r ~ O ~ ~ O
. ~ O O O O ~ er O -I O ~ O
O ~ ~ O O t~ ~ ~`J ') ~ _l t,) O O ~ O O O O O _l O O
~ _l _l ~ t~l _l ~r ~r _l ~r u~ O
u~ O ~1 O O ~1 O ~ ,~ O ,~ _l ~ u~ LO u~ u~ u~ ~n u~ Ln ~ m ~ ~ m m m m ~ m m ~
~, ~ o _, _, ~ ~7 ~ _, 1,. ' .

~77038 U o o o o o o o o o l o o .C ~ O O O O ~r ~ O ~r ~1 er O
cn ~ ~ O ~ ~r L~ u~ ~r In ~r u~ O
~ ~ ~r ~ ~ ~r ~ u~ ~r ~r ~ ~ O
u~ u~ ,1 ~ O ~ ~r In ~r In ~ Ln ~ ~r ~ ~1 O ~ ~r ul ~r ~ ~
a u~ ~ ~ o ~r ~r ~n er u~ ~r ~
O ~ ~ O O ~r er u~ ~ er ~ ~ ~
~ l I _l l l l l l I ~1 I O .' u~ ~: ~r O -~ ~1 ~ er ~r ~ er ~ ~r _1 .' ~ X o o o o o o o o o o o o a ~ 0 n ~r ,1 o ~r u~ ~ ~ Ln ~ ~ ~
H E~ ~.) et~ el~ I O O ~\ ~ O ~r r'l ~ ~
O E-~ P. _1 I O O O ~ O O O ~1 O O
~ el~ ~ O O ~I ~I ~r _l et~-~ ~r o ~ H O ~ O ') O 1~ 1~ ~ ~ t~l ~ O
1~ u~ r~) O O t~l _l ~ ~I ~'t ~r ~ O O
3 ~`I ~ O O ~ ~r ~r ~ ~ el' O

N O ~ --1 ~r ~r ~ ~ _I ~ O
3 O O ~ O O ~r ~1 ~ ~1 ~r ~ O
U~ O O -I ~ _~ ~ ~ er ~ ~ ~ O
C~ O O-I ,~ O ~ ~ _l ~ OO
~r: er O -I ~ ~ ~ ~r ~r ~r _l In _~
R ~ ~r _I O ~:r ~ ~r ~r ~r ~ _ _ _ ___ m m ~ m m m m m m ~ m ~1 ~ ~1 ~ ~ ~ u~ ~D 00 _ _ _ _ _ _ _ ~ ~

: ., ~.: . ' : '~ ':
- : . - : :
:: ; : -107703~
_ C~ o o o o o ~ o o o o O O er O ~ O U~ O O O
o ~ o ~ ~ U~ ~ er o F~ ~r~ O ~r ~ ,n N Ll-~ ~1 O 1~
U~ r~ ~ u~ ~ u~ ~ u~
r~ ~ ~ l u~ ~ u~
a O -I O ~r ~ ~ ~ ~ O O -1 R I ~r I ~ I ~r I ~1 I t~
U~ ~ ~ _~ ~ ~ el~ ~ In _l t'~l ~
~ ~ O O ~ ,1 O ~ O O O ~
a ~ ~ o ~ u~ er u~ ~ ~r ~r ~ ~r H E~ C~ _I ~ el~ ~ ~ ~ ~ ~ ~
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U~ I O O O ~ _~ I O ~1 _1 3 O O ~r O rl _l ~ O O -I

N O O ~r O ~1 ~1 ~r O O O
O ~I ~`J O O t~l ~ ~ O ~
~ O ~ ~ ~1 O ~ ~r ~ O ~1 C~ O -I O O O -I ~ _l O ~
a~ O ~, ~r ~ t~l ~ u~ _l O ~`I
O _l ~ _l O ~ Lr~ ~

m ~ m ~ m ~ ~ ~:
O ~I ~ In C~

.

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10~1~38 ~ o o o o o o o o o o ~ o o o ~ o o ~ o ~ o u~ ~ O ~ ~ ~r O n o Ln ~
~1 ~ O ~1 ~ ~r N Il~ er Lt') ~r v~ ~ O ~ ~r ~r ~ 11~ ~r Il~
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¢ U~ I O ~ O O I O I O
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~ O O O ~ O -I ~ ~I tY~ ~
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~ ~ _l _~ ~ _l _l Lr) I ~`I I
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~07703B
_ o o o o o o o o o o ~1 0 ~ O ~r ~1 O O O O
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u~ er ~ ~ U~ ~r n o ~
u~ ~r ~ n ~r u~ er ~ ~ ~ ~1 . ~ ~r ~ u~'~r u~ ~r ~ -I O
a ~r ~ ~ ~r u~ In ~ o ~ _, O ~ ~ ~r ~ ~ ~r O ~ O
~ I o I ~ I ~ I o I o u~ ~ ~r ~ ~r ~r ~ ~r u~ O ~1 0 æ x o o o ,~ o o o o o o b ~ o ~ ~ u~ ~ ~ ~ ~ o ~ o H E~ ~ O O ~ 'r ~ I _~ ~ O O
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el~ _l In ~r el~ ~1 ~ I ~
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~0770~8 _ t, o o o o o o o o o o ~
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u~ ~r ,1 u~ O In ~ ~ U~ ~1 Ul ~
~n ~ u~ ~ n ~ ~ n ~ Ln u~ ~ u~. ~ u~ ~r u~ u~ ~ I ~r . O U~ O Ln O In O ~ L~ er ~
~ ~o 10 10 l ~.o ,.,.
U~ ~ Ln ~1 ~ O U~ _l ~ In _l ~ ~r ~ X o o o o o o o o o o ~
:~ ~ ~ U~ O U~ O U~ ~ ~ U~ ~ er er H E~ O ~ O et' O ~r O _I ~r ~1 U~ ~r Z E-~ ~4 ~ O ~ O ~ O ~ ~ O 1. -1 ~ ~r I u~ I u~ I ~ u~ I u~

m H ~ l ~r O ~ ~`1 es' _~ ~ ~
U I O I O I O l I O U~ ~
~ er o ~ _1 ~r ~ O ~ ~

N ~ _( ~r O ~ O- N ~ _I ~ N
~ ~ N el ~ ~ ~ ~ ~ ~ _1 el .r O ~ N ~ N ~ ~ N ~ ~r C:~ N O ~1 _I ~J O --I ~ ~1 ~ er 1~ ~r O ul _I L(~ _I ~r In O N ~
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1077~3 _ o ~ o o o o o o o o o ~r ~ O O ~ O O O ~ O O
~n er rl ,1 Lf) ~ ~ O u~ ~ O
~ Ln er ~r ~ u~ ~ er ~r u~ ~ O
u~ u~ ~r ~ ~r Ln u7 L~ 7 In ~ O
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a I ~ l ~ u~ u~ ~ ~r u~ ~r o O ~r er ~r ~ ~ _l ~ O ~ _~

R
U~ ~ q' er ~ ~ el' O ~ ~ ~ er O
~ X O ~1 O O -~ O O O ~ ~1 O
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~ _I er ~ O ~ O ~1 ~ O ~I O
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C.~ u~ ~ O O O O O -I O ~ O
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r~
m m ~ m ~ ~q ~ m ~1 ~ ~r r~ ~ ~ ~ ~9 ~D ~D ~D ~D 1~ ~_ ~0 -- 56 ~

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~0770;~8 _ ~, o o o o o o o o o O ~ O ~ O ~r O ~ O
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u~ ~ ~ u~ ~1 u~ ~ ~ ~
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u~ ~ ~ u~ O ~r _l ~ I ~ I
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107'7038 The names of the test species are as follows:-Sb Sugar beet Rp Rape Ct Cotton Sy Soya bean Mz Maize Ww Winter wheat Rc Rice Sn Senecio vulgaris Ip Ipomoea purPurea Am Amaranthus retroflexus Pi Polygonum aviculare- .
Ca Chenopodium album Po Portulaca oleracea Ab Abutilon theoPhrastii Cv Convolvulus arvensis Ot/Av As in Example 3 Dg Digitaria sanguinalis Pu Poa annua St Setaria viridis Ec Echinochloa crus-galli Sh Sorghum halepense Ag Agropyron repens Cn Cyperus rotundus ., : , . -.
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.' ' , ~077038 ExAMæLE 5 This Example illustrates the selective herbicidal effects of compounds used in the process of the invention.
The compounds were formulated for test as described in Example 4. Tests were carried out on gxeenhouse plants as described in Example 4, except that the procedure in the pre-emergence test was somewhat different. In this test, the seeds were sown in a shallow slit in the soil, and the surface then levelled and sprayed. Fresh soil was then spread thinly over the sprayed surface. The results of the post-emergence test were assessed after two weeks and of the pre-emergence test after four weeks, on a scale of 0 to 9 where 0 is 0 to 10~ damage and 9 is 90 to iO0~
damage to the plant. The results are given in Tables VI, VII and VIII below.

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~0~703s Names of test plants:- .

Ww Wheat Br Barley Pe Pea Rp Rape Sb Sugar beet Lt Lettuce Av Avena fatua Al Alopecurus myosuroides Bt Bromus tectorum Ag Agropyron repens Sm Stellaria media Ca Chenopodium album Pi Polygonum aviculare Ma Matricaria inodora Sp Sinapis alba :-. . . . . . . :;

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Names of test plants:-Mz Maize Sy Soyabean Gn Ground-nut Ct Cotton To Tomato Po Portulaca oleracea Am Amaranthus retroflexus Ip Ipomoea purpurea Dt Desmodium tortuosum Ab Abutilon theoPhrasti Se Sesbania exaltata Co Cassia obtusifolia Si Sida sPinosa Ds Digitara sanguinalis Xa Xanthium ~ensylvanicum -, ,. .. :: : . .. :
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~, i~7~7038 The names of test plants not previously mentioned are as follows:-Rc Rice Sg Sorghum Ei Eleusine indica Ec Echinochloa crus-galli Dg Digitaria sanguinalis St Setaria viridis Sf Setaria faberii Sh Sorghum halepense Pm Panicum maximum Cn Cvperus rotundus . . : . ..
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This Example illustrates the selective herbicidal effect of compounds used in the invention in rice. A test was carried out in which the compounds were applied to greenhouse rice plants and weeds grown under simulated flooded paddy conditions. Twentysix days after treatment, the damage to the plants was assessed on the O to 9 scale used in previous Examples. The results are given in Table IX
below. It will be seen that while rice was substantially undamaged, the weeds were severely damaged at the rates of application used.

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~07~7~38 Names of test plants:-Ec Echinochloa crus-galli Lp Leptochloa dubia Cd Cyperus difformis Mv Monochoria vaginalis Sv Salvinia auriculata -.:: . ~ ; , . .

Claims (14)

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

1. A process of inhibiting the growth of unwanted plants, which comprises applying to the plants, or to the growth medium thereof, a herbicidally effective amount of a pyrimidine compound of formula (I):

(I) or an acid addition salt thereof, wherein R represents (a) a hydrogen atom; (b) a phenyl radical optionally substituted by one or more alkyl, alkoxy, fluorine, chlorine, or bromine atoms; or (c) an alkyl or alkenyl radical optionally substituted by one or more of the following: A fluorine, chlorine, or bromine atom;
a cycloalkyl, hydroxy, alkylthio, furyl, pyridyl, or mono- or di-alkylamino radical; a phenyl radical optionally substituted by one or more alkyl, fluorine, chlorine, bromine, phenyl, cyano, haloalkyl, or alkoxy radicals; or an alkoxy radical optionally substituted by one or more phenyl or alkoxy radicals; R1 repre-sents a lower alkyl radical; R2 represents a hydrogen atom or a lower alkyl radical; and R3 represents an alkyl or alkenyl radical optionally substituted by one or more of the following: Cyclo-alkyl; pyridyl; naphthyl; or phenyl optionally substituted by one or more fluorine, chlorine, bromine, iodine, haloalkyl, cyano, alkyl, hydroxymethyl, or 4-methyl-2-propyl-6-pyrimidinyl-oxymethyl radicals.

2. A process as claimed in Claim 1 wherein the group R is an alkyl radical of 1 to 6 carbon atoms, a benzyl radical, or a cyclohexylmethyl radical.

3. A process as claimed in Claim 1 or Claim 2 wherein the group R1 is a methyl radical.

4. A process as claimed in Claim 1 wherein the group R2 is a hydrogen atom.

5. A process as claimed in Claim 1 wherein the group R3 is an alkyl or alkenyl radical of 3 to 6 carbon atoms.

6. A process as claimed in Claims 1 or 2 wherein the group R3 is a benzyl radical optionally substituted by fluorine, chlorine, bromine or iodine.

7. A process as claimed in Claim 1 wherein the compound used in the process is one in which R is a propyl or allyl radical, R1 is a methyl group, R2 is a hydrogen atom, and R3 is a cyclohexylmethyl radical or a benzyl radical optionally sub-stituted by one or more fluorine, chlorine, bromine, or iodine atoms.

8. A process as claimed in Claim 1 wherein the compound used in the process is one in which the group R is a benzyl radical optionally substituted by fluorine, chlorine, bromine, or iodine, R1 is a methyl radical, R2 is a hydrogen atom, and R3 is a propyl or isobutyl radical.

9. A process as claimed in Claim 1 wherein the pyri-midine compound is applied at a rate of from 1 to 10 kilograms per hectare.

10. A process of selectively inhibiting the growth of weeds in crops of soya bean, ground nut cotton, wheat, barley, and rice, which comprises applying to the crop area, before the crop emerges, a compound of formula (I) as defined in Claim 1, in an amount sufficient to inhibit the growth of the weeds, but insufficient substantially to damage the crop plants.

11. A process as claimed in Claim 10 wherein the rate of application of the pyrimidine compound is from 1 to 4 kilograms per hectare.

12. Herbicidal pyrimidine compounds, having the formula (I):

(I) and acid addition salts thereof, wherein R represents (a) a hydrogen atom; (b) a phenyl radical optionally substituted by one or more alkyl or alkoxy groups of 1 to 4 carbon atoms or fluorine, chlorine, or bromine atoms; or (c) an alkyl or alkenyl radical of up to 12 carbon atoms optionally substituted by one or more of the following: A fluorine, chlorine, or bromine atom; a cycloalkyl group of 3 to 6 carbon atoms, a hydroxy group, an alkylthio group o. 1 to 6 carbon atoms, a furyl or pyridyl radical, a mono- or di-alkylamino radical in which the one or two alkyl radicals each contain from 1 to 6 carbon atoms;
a phenyl radical optionally substituted by one or more alkyl, haloalkyl, or alkoxy radicals each of 1 to 6 carbon atoms, or fluorine, chlorine, bromine, phenyl, or cyano; or an alkoxy radical of 1 to 6 carbon atoms optionally substituted by one or more phenyl radicals or alkoxy radicals of 1 to 6 carbon atoms;
R1 represents an alkyl radical of 1 to 3 carbon atoms; R2 represents a hydrogen atom or an alkyl radical of 1 to 4 carbon atoms; and R3 represents an alkyl or alkenyl radical of up to eight carbon atoms, optionally substituted by one or more of the following:

cycloalkyl of 3 to 6 carbon atoms; pyridyl; naphthyl; or phenyl optionally substituted by one or more fluorine, chlorine, bromine, iodine, haloalkyl or alkyl each of 1 to 4 carbon atoms, cyano, hydroxymethyl, or 4-methyl-2-propyl-6-pyrimidinyl-oxymethyl radicals; provided that when R is hydrogen or methyl, R3 is not an alkyl radical of 1 to 4 carbon atoms or a benzyl radical.

13. Compounds of the formula defined in Claim 12 wherein R is a propyl or allyl radical, R1is a methyl group, R2 is a hydrogen atom and R3 is a cyclohexylmethyl radical or a benzyl radical optionally substituted by one or more fluorine, chlorine, bromine, or iodine atoms.

14. Compounds of the formula defined in Claim 12 wherein R is a benzyl radical optionally substituted by fluorine, chlorine, bromine, or iodine, R1 is a methyl radical, R2 is a hydrogen atom, and R3 is a propyl or isobutyl radical.