CA1057290A - 3-pyridylmethyl aryl urea rodenticides - Google Patents

Abstract

ABSTRACT
Novel 1-(3-pyridylmethyl)-3-(4'-substituted-phenyl or -naphthyl) ureas. The 4'-substituent may be -NO2, -CN, CF3, -C(O)R1, -SR2, -SO2C6H5 or -SO2NR3R4.
These compounds are biologically active, and many are active rodenticides.

Description

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The Disclosure The present invention relates to novel 1-(3-pyridylmethyl)~3-(~'-substituted-phenyl or -naphthyl)ureas.
~ These compounds possess desirable biologically active ; 5 properties, such as bactericidal, fungicidal, herbicidal, insecticidal and rodenticidal properties.
' The present invention is also concerned with ~ ' rodenticidal compositions containing preferred 3-pyridylmethyl ~'-phenyl or naphthyl ureas having exceptionally strong ~' .
rodenticidal action and their use for the control and extermination of pest rodents.
, ' The common rat, Rattus norve~icus, is vicious and ;-constantly poses a serious threat to the health and well- '~
being of man. Rats and mice are destructive animals and a ~;
~ . .
serious nuisance, causing millions of dollars damage annually to homes~ farms~ agronom:ic crops7 food processing plants and many other businesses~ Rats bite at least 14,000 (possibly up to 60,000) people in the United States every year, according to the U. S. Public Health Service~ '' -and are known carriers of over 35 contagious diseases including ' '`
bubonic plague7 trichinosis~ typhus~ rat bite fever~ amoebic - ~ -dysentery~ tuberculosis, infectious jaundice and rabies. ''~
... ~ . .
During the years from 1898 to 1923, almost 11 million deaths ~ ~ ' were caused by rat-borne plagues.
Use of rodenticides~ fumigants~ sprays and traps are the primary methods employed f'or the control of pest ' rodents. By "pest rodents" we refer not only to members `
of the order Rodentia but also to those of Lagomorpha7 which cause'health hazards or economic loss unless kept in check.~ '' Rodenticides may be used in the form of a tracking powder '' i ~ .

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or a bait or may be applied as a spray on -the rodent's natural foodstuffs. The rodenticides used as a bait are of two classes: single-dose and multi-dose. Multl-dose rodenticides have usually been preferred to single-dose rodenticides, as they have generally been safer than the single-dose roden-ticides heretofore available. The multi-dose rodenticides,such as 4-hydroxy-coumarin and 1~3-indandione compounds, are anti-coagulants generally. These multi-dose rodenticides when consumed in small daily amount have a lethal effect (generally caused by internal bleeding) on rats and mice after depletion of vitamin K stores in the liver. Anti-coagulant types of roden-ticides are less effective on mice than rats, as mice are considered to be nibblers and do not usually consume an adequate amount o~ treated bait to have a lethal effect. A ;
single-dose rodenticide which would be relati~ely safe to the person handlin~ the material and to non-target species of animals and yet effective on a variety of pest rodents is `- ~;
highly desirable. ;
Many compounds are toxic to rodents. However~ very few of these compounds are anywhere near suitable for use as a rodenticide because it is necessary for the pest rodent to consume voluntarily a sufficient amount of the poison even though sufficient untreated food may also be available. In rodenticides used as bait or as a spray, feed acceptance is the key to excellence~ and in all rodenticides safety and efficacy are highly important.
The 1-(3-pyridylmethyl)-3~ substituted-phenyl or -naphthyl)ureas of the present invention are so highly toxic to a wide ~ariety of pest rodents that a single dose is sufficient; yet many of them are relatively safe for use in / ~

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the presence of other species which may inadvertently ingest limited quantities of the rodenticide. Furthermore~ rats - and other pest rodents willingly consume the compounds of the present invention in sufficiently lethal arnounts when present in baits. Alternatively, the compounds may be employed in composi-tions to be sprayed on natural foodstuffsO
They may also be employed in tracking powder, e~specially for use against mice, which habitually clean their paws by licking.
The compounds of the present invention have the -. formula:

O ', ~, :
. ~ CH2-NH-C-NHAryl (I) - N

wherein Aryl i.s ~ X or ~ X wharein ~- . X is selected from the group consisting of -N02, -CN, -CF3, :
,; . . . . . , . . - - ~
-c (o) Rl wherein Rl is an alkyl group of 1-4 carbon atoms, ~ ;
~SR2 wherein R2 is hydrogen or alkyl of 1 to 6 carbon atoms)or .

-s02Y wherein Y is -C6H5~or -NR3R4 wherein R3 and R4 are hydrogen, methyl or ethyl.
Of these compounds~ the preferred ones are those :; `~
in which Aryl is ~ X and especially those in which X
: is -C(O)CH2CH2CE~3~ -CN, -N02 or -SCH3~ The most preferred .
. compound is 1-(3-pyridylmethyl)-3-(~-nitrophenyl)urea. .:
; It is to be noted that the X-substituents on the phenyl or naphthyl ring are highly electron-withdrawing except r ~3 r~
:
7~
for the -SR2 groups.
The present invention, in another aspect, resides in a process for producing a rodenticidally active 1-(3-pyridylme~hyl)-3-(4'-substituted-phenyl or-naphthyl)urea :
of the formula o ~ CH2NH--C-NHA~

N

wherein Aryl i5 ~ or ~ ~

~ ~',", .

which comprises the steps of Cl~ either (A) reacting `
approximately equimolar amounts of a p-substituted phenyl or naphthyl isocyanate ~nd 3-aminomethyl-pyridine, the ::~
prsubstituent X ~eing seIected from -N02, -CN, CF3, -C(01R
wherein Rl is an alkyl group of 1 to 4 carbon atoms, -SR2 wherein R2 is hydrogen or an alkyl group of 1 to 6 car~on . - . -.
atoms, or -S02Y wherein Y is ~C6H5 or NR3R4 wherein R3 and R4 ~
are hydrogen, methyl or ethyl; in the presence of an inert ~ ~.
: solvent under substantially anhydrous conditions; or (B) ,~
reacting approximately equimol r amounts of an aniline of the formula ~ .

H~N ~ ~ X or H~N ~ X

wherein X is as defined above, and phenyl N-~3-pyridylmethyl) carbamate in the presence of a polar solvent; and (2) recovering the solid product by filtration. :

~5~ :

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In still another aspect t~e present invention resides in a method of exterminatin~ pest rodents which comprises exposing a rodenticidally effective amount of a rodenticidal composition comprising a compound as previously defined, or ; -a mixture of two or more such compounds, in association with one or more auxiliary substances of the type convention-ally used in such a composition, in the vicinity of a population of said pest rodents in a place where it may be easily reached and ingested by said pest rodents. `
~he literature is rathex sparse with respect to 1-(3-pyridylmethyl)-3-(aryl)ureas which are frequently named

3-picolyl)-3-~aryl)ureas. Hamilton and Sculley in J. American Chemical Soc. 75, 3400(1953) reported on the ~`
chemistry of a l-(3-picolyl)-3-phenylurea having various -~
,,. ,: .
substituents on the picolyl nucleus U. S. Patent 3,700,678 is concerned with l-methyl-l-picolyl-3-aryl ureas useful for `~
controlling undesirable vegetation.
The ureas of the present invention may be prepared by permitting approximately equimolar amounts of substituted phenyl isocyanate and 3-aminomethylpyridine to react in the presence of an inert solvent, e.g., acetonltrile, benzene, : .
toluene or 1,2-dimethoxyethane (glyme). Examples 1, 4 and 10 describe the preparation of compounds of the present invention in this manner. Table I below gives the physical constants - for the aryl isocyanate intermediates (which are made from ~-the corresponding X-substituted anilines~ used in their ;`
preparation.

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TABLE I
ArylNCO Intermedia-tes Used in Aryl = Melting point (C) or Example soiling point (C/pressure mm.) 6 4 2 a commercial product

4 -C6H4SH 56-61/0.85 ;~
C6 4SCH3 4 68/0.15 6 -C6H4SC2H5-4 52-60/0.3 7 -C6H4(SC3H7 n)-4 53-54/0.25 108 -C6H4(SC4Hg-n)-4 105-109/0.35 9 -C6H4(SC4H9-seC)-4 110/0.25 - ~-C6H4(SC4Hg t) 4 86/0.45 11 -C6H4(sc6Hl3-n)-4 112-117/0.25 12 -C6H4C(O)CH3 Oila ;
13 -C6H4c(O)cH2c~3 ila 14 -C6H4C(O)CH2CH2CH3-4 ila :,~ ., 16 -C6H4SO2N(C2H5)2 150-153/0.3 17 4-nitronaphthyl oila ~
1,, ~ ,, a) identified by infrared spectra - all giving a strong ` -~
-N=C=O band at 4.3 to 4.6 ~.

- Alternatively the ureas may be prepared by permitting ~
approximately equimolar amounts of the X-substituted aniline and ~ -a carbamate, such as phenyl N-(3-pyridylmethyl)~carbamate, to react in a polar solvent such as ethanol. Example 2 describes ~-the preparation of one of the compounds of the present invention in this manner.

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Pre~aration of ~ -pYridylmeth~ -nitrophenYl)urea A solution of 415 g. of crude p-nitrophenyl isocyanate in 4.5 lo of toluene was stirred at room temperatureO The mixture was filtered and 35 g. of insoluble impurity removed. The material in solution was 380 g.
(2.32 mol) of purified p-nitrophenyl isocyanate. The solution was stirred under dry nitrogen, and 3-(aminomethyl)-pyridine (250 g.~ 2.32 mol) was added dropwise. An exotherm to ~OoCO was noted. The resulting thick suspension was stirred overnight and thèn vacuum filtered. The product was ~ . ~
washed with hexane and dried in a vacuum oven at 60oC. over-night to give 61007 g. ~elting at 220-221~5Co The product was a 98% yield of 1-(3-pyridylmethyl)-3-(~-nitrophenyl)urea. ~
This product after recrystallization from 2-methoxyethanol ~ ; -melted with decomposition at 223-2250C.
Example 2 Prep~ration of l-(~-p~ridylmeth~ -cyanophenyl~urea The intermediate phenyl N-(3-pyridylmethyl)-,;, ~ ~.
~ 20 carbamate was prepared as follows: -. , ~ solution was prepared of 3-aminomethylpyridine `
(21.6 g.~ 0.2 mol) and triethylamine (22.2 g., 0.2 mol) in 150 ml. of anhydrous ether. A solution of phenyl chloro-formate (31.~ g., 0.2 mol) in 100 ml of dry ether was -added dropwise in 20 minutes. The resultant suspension was ;~
, ~
stirred for 30 moré minutas, then was vacuum-filtered to remove triethylamine hydrochloride. The filtrate~ when cooled~ gave 4.1 g. of the desired carbamate melting at 88-90OC. The second filtrate, when evaporated~ afford 25 g. of the product in a slightly impure condition melting '',,., ' ~,' ' : , ' ': ' . . ` ' ::' ~ . ' . .. , . ~ `

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at 75-850C. The triethylamine hydrochloride was dissolved in water~ and the aqueous solution was then extracted with methylene dichloride. The dried methylene dichloride extract was evaporated to give 11 g. of product melting at 82-850C~ -Total crude yield of phenyl N~(3-pyridylmethyl)carbamate was 40.1 g. or 89%o The urea was then prepared from the carbamate as follows:
To a solution of phenyl N-(3-pyridylmethyl)-carbamate (10.9 g., 0005 mol) in 150 mlO of anhydrous ethanol there was added p-aminobenzonitrile (5.7 ga ~ 0.05 mol).
The mixture was refluxed for 5 hours~ cooled, and evaporated under reduced pressure to yield a dark oil. This oil was ;-dissolved in ether~ and this solution was washed three `
times with 50 ml. portions of 5% NaOHO After drying of the ether solution and evaporation of the solvent~ a yellow oil was obtained which was placed under high vacuumO A
small quantity of material sublimed while the residue in the flask cr~stallized. Recrystallization from eth-yl acetate gave 5.2 g. of white crystals melting at 184-187Co This was ~ -a 43% yield of 1-~3-pyridylmethyl)-3-(4-cyanophenyl)urea.
; Example ~ ;
`~ Preparation of 1-(3-PyridYlmeth~l)~~ mercaPt~hen~yl~urea ^ (a) Preparation of ~-mercaptophenyl isocyanate ` ;
A reaction mixture consisting of molar ,,,1 .
quantities of t-butylmercaptan~ potassium hydroxide and~ -~
- p-chloronitrobenzene in 1~2 1. of ethanol was stirred for -days at room temperature to ~50C and then filtered. The filtrate was poured into water and extracted with methylene dichloride to give 161 g. of a brown oil which is a 76%
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weight yield of crude 4-(t-butylmercapto)nitrobenzene.
To a suspension of 4-(t-butylmercapto)nitrobenzene (52.8 g.g 0.25 mol) and iron powder (150 g.) in 1 1. of water there was added 1 ml. of acetic acid. The reaction mixture was stirred 18 hours at 90~C~ and filtered. Both the . .-:
residue and filtrate were extracted ssveral times with methylene dichloride, and the combined dried methylene ;-~
dichloride extracts were concentrated at reduced pressure to give 18.2 g. of a brown oil. This is a 40% weight yield of 4-(t-butylmercapto)aniline, To this oil in 100 ml. of benzene there was then added dropwise 158 g. of a 12.5~ ~ ~
benzene solution of phosgene (0.2 mol) with cooling. The ~ -reaction mixture was stirred for 1 hour at 10C.~ overnight at room temperature and then at reflux temperature for 7 hours~ After standing overnight the reaction mixture was filtered~ the filtrate concentratecl at reduced pressure~ then vacuum-distilled. Two product fractions were collected as (1) 2 g. distilling at 56-61C./0.85 mm. ~-and (2) 2 g. distilling at 86~C./o,45 mm, - ~ ~-~.. ...
Fraction 1 is 4-mercaptophenyl isocyanate and Fraction 2 is ``
4-(t-butylmercapto)phenyl isocyanate.
b) Preparation of 1-(3-pyridylmethyl)-3-(4-mercaptophenyl)urea To 4 mercaptophenyl isocyanate (0.9 g., 0.006 mol) in 50 ml. of anhydrous benzene was added 3-pyridylmethylamine ;` ~ -(0,65 g.~ 0.006 mol). An exothermic reaction caused the temperature to rise to 400C and a white precipitate formed.
The reaction mixture was momentarily heated to reflux~ then cooled to room temperature and filtered to give 1.2 g. melting at 155-159c. The product was a 77.~% yield of 1-~3-pyridyl-methyl)-3-(4-mercaptophenyl)urea.
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Ex~ ~le 10 Preparation of 1-(3-pyridylmeth~1)-3-(4-t~butyl~ercaptophenyl)-urea To a 4-(t-butylmercapto)phenyl isocya~ate (1 g.
0~005 mol; see Example ~ above) in 50 ml. of anhydrous benzena there was added 3-pyridylmethylamine (C.52 g.~ 0.005 mol). The temperature rose to 400C. and a prec-'pitate formed. The raaction mixture was heated to reflux for a very short time then cooled and filtered to give 1.5 g. of solid melting at 154-157.50C. The product was a 98~ yield 1-(3-pyridylmethyl)-3-(4-t-butylmerca~to)phenylurea.
Table II~ concarning "3-PyridylCH2NHC(~)NHAryl-X
Compounds"~ gives the physical constants and analytical data for typical examples of this invention. In this table the column headings have the following meanings: Ex~ is Example No., X is the ~-substituent in the phen~l nucleus (or naphthyl for Example 17), MoPo is Melting Point (Examples 1 and 17 are with decomposition), Emp. Form. is Empirical Formula and "%C", "%H" and "%N" are analytical data (the number in parentheses represents the theoretical value as calculated from the empirical formula).~ 7, ....

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H h 'i'' E~ ~ ~ ~ V~ C)~ V~ C7~ ~)~ V~ C~ ~ V~ " ~ ~

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X N r-l ~1 i--I r~ r~ ~ i~ ~ r~
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~S7290 The novel 1-(3-pyridylmethyl)-3-aryl ureas of the invention are biologically active and may be useful as bactericides, fungicides especially for phytopathogenic fungi~ insecticides, rodenticides and herbicldes.-.

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The follo~ing description describes the use of ~ -the compounds of the inventio~ as a rodenticide.
Formulation for use as a rodenticide ~-The compounds of the present invention may be ~-formulated into rodenticidal compositions such as baits, tracking powders, and spraysO A bait may, besides the tox-icant, comprise a basal ration, such as a carrier usually edible optionally with a preservative to prevent insect infestation, mold growth or rancidity. The carrier may be a semi-moist materiala such as canned cat or dog food or garbage including apples, eggs~ bacon, etc.~ but it is generally prePerred to use a dry carrier as this remains ~ ~
acceptable for longer periods. The dry carrier may be a ~-;
- combination of natural food products such as whole ground corn, steel cut oats, sugar~ molasses, rice, vegetable oil~ salt~ dehydrated fruit~ fish meala tankage or wheat.
; When necessary to use in d~mp locations, the basal ration may include a binder to form the composition into a matrix. ~;
The binder may be a water repellent material, such as a ~ ~ ~ t ~ paraffin wax or an acrylic polymer.
The compounds of the present invention may be ~ ;
incorporated as a toxicant in bait formulations, either alone or in combination with other toxicants. When used as the -sole toxicant 1n baits1 the compounds of the present invention may be used in any rodenticidally effective concentration.
Depending on the susceptibility of the rodents to the toxicant and the amount of formulated bait generally consumed~ concentrations as low as 0.01% may be employed.
A typical bait may contain between about 0.5% and 2.5% of the toxicant by weight. It has been found that there is no , ~s~z~ :
upper limlt to tne amount of compound which may be present in a bait and that a bait consisting almost entirely of one of the present compounds can be ingested in a rodenticidally sufficient quantity. Example 18 describes the formulation of a suitable bait~ although wide variations in formulation may be made for different conditions of use.
Tracking powders~ which are particularly effective against mice~ may be either a compound of the present invention in finely powdered form or a mixture of the compound with a powdered carrier, e.g.~ talc~ sugar, milk powder, Indian corn meal~ fish meal~ cornstarch~ flour~ ~;
and bentonite, or the like, or any combination thereof which tends to induce the animals contaminated with the preparation to lick themselves more thoroughly. In tracking powders~
the compounds of the present invention may be incorporated in amounts from 100% down to 0.75% by weight, or somewhat less with proper formulation. Exarnple 19 describes the preparation of a suitable tracking powder.
Spray concentrations may be made by dissolving the compoundsof this invention in a solvent. In general, the 1-(3-pyridylmethyl~3-aryl ureas have a limited solubility~
i.e. between 1 and 15%. Solvents which are useful for making a spray strength solution include alcohols such as ethanol and 2-methoxyethanol~ ketones such as acetone, dimethylformamide~ dimethyl sulfoxide and pyridine. In general a rather volatile solvent is preferred when a solution -`
is to be sprayed onto a natural food source of the rodents, ~so that the solvent will be rather rapidly removed and the ~-toxicant is deposited in an essentially unadulterated form onto the food.

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Each of the compounds of Examples 1 to 17 was blended with the basal ration in a Waring laboratory blender ~;
to form 50 grams of a homogeneous premix. The amount of compound utilized is determined by the percentage of active material desired in the feed. The formula for ths basal ration is shown below, all percentages being by weight:
Crude ground corn 65% -~
Steel cut oats 25%
Powdered sugar 5%
Corn oil 5~ ;
The 50 grams of premix containing the toxicant ~
were then mixed with an additional 450 grams of basal - ~ -rationO These components are mixed in a Little Ford Lodige mixer for three minutes.
Exam~le 19 TrackinÆ_Powder The active compound is finely pulverized by mortar and pestle to form a 100%-active tracking powder. To form ~-~
a 5% actlve materlal, it may be mixed with lOX confectioner's sugar in a 1 to 19 ratio and at other ratios for other levels of active compound.
Rodentlci-dal_evaluations ~ ~
a) Preliminar evaluations ; ~ `
One~preliminary evaluation is on the albino mouse, (Mus musculus). In such a test, four caged laboratory albino mice are fed a diet containing the test compound at 1000 parts per million (ppm) for 1~ days. On each of the llth~ 12th and 13th days there is also orally administered to the surviving mice~ the toxicant in a 005% aqueous methyl cellulose solution at a dosage of 200 mg./kg. The `, ' ''' ' , ' ' , :
. : . . .
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number of mice that died up through the 10th d~y of feeding and the total that died d-uring the 14-day test period were recorded.
The compounds were preliminarily evaluated for their ability to kill albino rats (Rattus norvegicus) by oral administration to two rats at a dosage of 50 mg./kg.
and sometimes at 200 mg./kg. The effect on the rats was observed 14 days later. If at least one of the rats had died, the compound was then subjected to secondary tests.
Table III gives the results.
~able III -Preliminar~ Rodenticidal Activit~*
Acute Oral Toxicity Albino mice Albino rats ~ oral dosage 50 mg/kg 200 mg~kg, fed lO daysfor 3 days at ;~ on 1000 P~m? m~ .
1 1/~ 4/~ 2/2 2 2/~ 2/2 3 0/~ - 2/4 1/2 ~ o/~ o/4 0/2 `~
0/4 1j4 l/2 `,~
6 0/4 0/~ 0/2 l/2 7 0/4 0~4 0/2 0/2 8 l/4 3i4 0/2 0/2 11 0/4 - l/2 12 ~ 0/2 ~ `~

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Table III ~ t'd) Acute Oral Toxicity Albino mice Albino rats ~ oral dosage 50 mg/kg 200 mg/kg O ' , fed 10 days for 3 days at Example on 1000 ppm 200 m~./k~.
0/1~ 0/~ 1/2 16 0/1~ 2/4 1/2 17 __ __ 1/2 ' ' ''' * Data given as rodents killed/rodents tested.

b) Secondary evaluations On~ of the most significant secondary tests is a standard one known as the paired-preference test. In , this test the rodents are given a free choice between the treated and untreated bait, Such a test most nearly approximates practical use conditions, `~
The rodents were caged individually, and were provided with dual feed cups and separate water devices. The , .-:~ , basal ration was offered in excess of daily feed require-ments in each of two feeders one treated with the test compound and one without. For each test~ equal numbers of each sex were used.
The gross weight of each feed container and its feed were determined daily and returned to the starting weight by addition of complete replacement of the given diet. The position of the bait and the laboratory diet cups in the cage were reversed every 2~ hours to counter ~ ;~
any feeding position habit of the rat. The test rodents had free choice between treated and untreated feedO Mortal-ities were recorded daily, 3LC)57;~

To meet the criteria for a singla-dose product, a rodenticide in this initial test must kill 75% of the rats within 8 days 7 where the poison bait is available for :the first 72 hours of this period~
The results of representative paired-preference tests with several examples on individually-caged rodents .
are given in Table IV.
Table IV
Paired-Preference Tests Example Rodent Compound in Rodents killed/
Basal Ration Rodents tested .
_ ~ppm) 1 albino rat 100~000 1/4 (Ra.ttus norvegicus) 50~000 1/2 . ` ~ -10,000 2/2 and 3/L~
3~000 2/2 . ::
500 /2 and l/

1 Norway rat lO~OOOa 9/1Oa .. :
(Rattus norve~icus) .
1 roof rat 10,000 3/4 (Rattus rattus) 1 feral mouselO,OOOb l/L~ ..
(~us musculus)10~000C L~/~
; 25 1 deer mouse ~10~000 L~/
(Perom.vscus ~}~) 1 meadow vole 10,000 0/~ ;~
(Microtus _eucopus) 2 albino rat 3~000 1/2 ~ -3 albino rat 3~ooo 0/2 albino rat 50~ooo 1/2 .-.
10~000 2/2 3~000 1/2 ~ .;
16 albino rat 3~000 0/2 .
: 35 a) This evaluation was run as a one-day~ single-bowl test.
b) This bait used the product of Example 1 melting at ;
~ .

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72~
220-221.5C. ~;
c) This bait used the pxoduct of Example l melting at 223-2250Co ; When evaluated by the preliminary evaluation technique described above, the following structuresvery closely related to the highly active Example l, 1~(3- ~.
pyridylmethyl)-3-(4-nitrophenyl)urea~ were devoid of activity:
1-(2-pyridylmethyl)-3-(4-nitrophenyl)urea 1~(4-pyridylmethyl)-3-(4-nitrophenyl)urea 1~(3-pyridylmethyl)-3-(4-nitrophenyl)thiourea l-methyl~1-(3-pyridylmethyl)-3-(~-nitrophenyl)urea -1-(3-pyridylmethyl)-3-methyl-3-(4-nitrophenyl)urea It is concluded that a very exacting structure is required ~::
; 15 to achie~e excellent rodenticidal activity~
It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined hereinO :~

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Claims (21)

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

1, A compound having the formula wherein Aryl is or wherein X is selected from the group consisting of -NO2, -CN, CF3, -C(O)R1 wherein R1 is alkyl of 1 to 4 carbon atoms, -SR2 wherein R2 is hydrogen or alkyl of 1 to 6 carbon atoms or -SO2Y wherein Y is -C6H5 or -NR3R4 wherein R3 and R4 are hydrogen, methyl or ethyl.

2. The compound of claim 1 wherein Aryl is .

3. The compound of claim 2 wherein X is -NO2.

4. The compound of claim 2 wherein X is -CN.

5. The compound of claim 2 wherein X is -SCH3.

6. The compound of claim 2 wherein X is -C(O)CH2CH2CH3.

7. A method of exterminating pest rodents which comprises exposing a rodenticidally effective amount of a rodenticidal composition comprising a compound as defined in claim 1, or a mixture of two or more such compounds, in association with one or more auxiliary substances of the type conventionally used in such a composition, in the vicinity of a population of said pest rodents in a place where it may be easily reached and ingested by said pest rodents.

8. The method of claim 7 wherein said rodenticidal composition is a bait.

9. The method of claim 7 wherein X is -NO2.

10. The method of claim 9 wherein the place where said rodenticidal composition is exposed is also easily reached by animals other than pest rodents, whereby the pest rodents are selectively exterminated and the other animals are unharmed.

11. The method of claim 10 wherein said rodenticidal composition comprises between about 0.5% and 2.5% by weight of the compound, and an edible carrier selected from whole ground corn, steel cut oats, sugar, molasses, rice, vegetable oil, salt, dehydrated fruit, fish meal, tankage, wheat, paraffin wax, and acrylic polymer, and mixtures thereof.

12. The method of claim 7 wherein said rodenticidal composition is exposed for a period of about 3 days and then removed.

13. The method of claim 7 wherein said rodenticidal composition is a tracking powder and is placed in an area upon which said pest rodents customarily step.

14. The method of claim 13 wherein X is -NO2.

15. A process for producing a rodenticidally active 1-(3-pyridylmethyl)-3-(4'-substituted-phenyl or-naphthyl)urea of the formula wherein Aryl is or which comprises the steps of (1) either (A) reacting approximately equimolar amounts of a p-substituted phenyl or naphthyl isocyanate and 3-aminomethyl-pyridine, the p-substituent X being selected from -NO2, -CN, -CF3, -C(O)R1 wherein R1 is an alkyl group of 1 to 4 carbon atoms, -SR2 wherein R2 is hydrogen or an alkyl group of 1 to 6 carbon atoms, or -SO2Y wherein Y is -C6H5 or NR3R4 wherein R3 and R4 are hydrogen, methyl or ethyl; in the presence of an inert solvent under substantially anhydrous conditions; or (B) reacting approximately equimolar amounts of an aniline of the formula or wherein X is as defined above, and phenyl N-(3-pyridylmethyl) carbamate in the presence of a polar solvent; and (2) recovering the solid product by filtration.

16. The process of claim 15 wherein in the first step, procedure (A) is followed.

17. The process of claim 16 wherein the inert solvent is selected from the group of solvents consisting of benzene, toluene, acetonitrile and 1,2-dimethoxyethane.

18. The process of claim 17 wherein the p-substituent is nitro.

19. The process of claim 17 wherein the p-substituent is mercapto or (C1-C6-alkyl) mercapto.

20. The process of claim 15 wherein in the first step, procedure (B) is followed.

21. The process of claim 20 wherein the polar solvent is ethanol.