This invention concerns certain 3-(3- or 5-substituted-5- or -3-yl)-1-substituted-1-(2,2-substituted)ureas having herbicidal activity, and their use to control weeds.

FIELD OF THE INVENTION 
This invention concerns certain acetal ureas, and in particular, 3-(3- or 
5-substituted isoxazol-5- or 3-yl)-1-substituted-1-(2,2-substituted)ureas 
having herbicidal activity, and their use to control weeds. 
DESCRIPTION OF THE INVENTION 
This invention relates to 3-(3- or 5-substituted-isoxazol-5- or 
-3-yl)-1-substituted-1-(2,2-substituted)ureas represented by the formula: 
##STR1## 
wherein: A is 
##STR2## 
wherein R is alkyl or haloalkyl of up to 6 carbon atoms; cycloalkyl of 
from 3 to 8 carbon atoms; alkenyl or alkynyl of up to 5 carbon atoms; 
--R.sup.4 --O--R.sup.5 or --R.sup.4 --S--R.sup.5 wherein R.sup.4 is 
alkylene of up to 6 carbon atoms and R.sup.5 is alkyl of up to 6 carbon 
atoms; or 
##STR3## 
wherein Z is nitro, halogen, trifluoromethyl or R.sup.5, and n is 0, 1, 2, 
or 3; 
R.sup.1 is alkyl of up to 3 carbon atoms or allyl; 
R.sup.2 is hydrogen, hydroxy, alkyl of up to 4 carbon atoms, or allyl; and 
R.sup.3 and R.sup.6 are the same or different alkoxy or alkylthio of up to 
6 carbon atoms or R.sup.3 and R.sup.6 may join together to form a 5 or 6 
membered heterocyclic ring containing up to 3 hetero, i.e., oxygen or 
sulfur, atoms. 
Some alkyl groups of which the various constituents in the above formula 
are representative are, for example, methyl, ethyl, n-propyl, iso-propyl, 
n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, or the like. 
Exemplary alkoxy and alkythio groups are methoxy, ethoxy, propoxy, butoxy, 
methoxyethyl, methylthio, ethylthio, butylthio, and the like. As examples 
of cycloalkyl groups there may be mentioned cyclopropyl, cyclobutyl, 
cyclopentyl, cyclohexyl, cyclopentyl, and cyclooctyl. Allyl, butenyl, 
pentenyl, propynyl, butynyl, pentynyl, and the like are exemplary of 
suitable alkenyl and alkynyl groups represented in the above formula. 
Representative suitable alkylene groups are, for example, methylene, 
ethylene, propylene, butylene, pentylene, or hexylene. As the halogen 
substituents, there may be mentioned chlorine, bromine, iodine, or 
fluorine, preferably chlorine or bromine. 
Although any compound within the scope of the above formula is believed to 
have herbicidal activity in accordance with this invention, those 
compounds that have been found to be especially efficacious are 
3-(5-t-butylisoxazol-3-yl)-1-methyl-1-(2,2-dimethoxyethyl)urea and 
3-(5-t-butylisoxazol-3-yl)-1-methyl-1-(1,3-dioxolan-2-yl methyl)urea. 
The compounds of this invention may be conveniently prepared by 
phosgenating a 5-substituted-3-aminoisoxazole of the formula: 
##STR4## 
or by reacting a 3-substituted-5-amino isoxazole of the formula: 
##STR5## 
wherein R is as previously defined with phenyl chloroformate, to prepare 
the corresponding isocyanate or phenyl carbamate, respectively. The 
isocyanate or carbamate is then reacted with an equivalent amount of an 
appropriately substituted amino acetaldehyde acetal of the formula: 
##STR6## 
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.6 are as previously defined, 
to form a compound of the invention. The preparation of the acetal urea 
compounds of the invention is more completely described in U.S. Pat. No. 
4,268,679, the teachings of which are incorporated by reference herein. 
The following Examples are illustrative of the synthesis of certain 
specific compounds of this invention.

EXAMPLE 1 
Preparation of 
3-(5-t-butylisoxazol-3-yl)-1-methyl-1-(2,2-dimethoxyethyl)urea: 
(a) A 300 milliliter, 3-neck flask equipped with a magnetic stirrer, 
thermometer, and dry ice condenser/drying tube was charged with 100 
milliliters of ethylacetate solution containing 4.8 grams (0.034 mole) of 
3-amino-5-(1,1-dimethylethyl)isoxazole. Anhydrous hydrochloric acid gas 
(10.0 grams) was bubbled into the solution, and then 20 grams of phosgene 
was bubbled into the solution, which was cooled in an ice bath. The 
solution was allowed to stand at ambient temperature for 17 hours and then 
the flask was purged with argon until no COCl.sub.2 was detected. The 
solution was filtered under nitrogen, and the precipitate was washed with 
benzene to give a precipitate containing about 0.034 mole (5.6 grams) of 
5-(t-butyl)isoxazol-3-yl isocyanate. 
(b) At ambient temperature, 4.2 grams (0.035 mole) of 
methylaminoacetaldehyde dimethylacetal in 15 milliliters of benzene was 
rapidly added to 50 milliliters of benzene solution containing 0.034 mole 
(5.6 grams) of the precipitate of 5-(t-butyl)isoxazolyl-3-yl isocyanate 
(prepared above). The resulting slurry was heated to reflux for two 
minutes, filtered, cooled, and 20 milliliters of hexane added, but no 
crystals formed upon standing and cooling in a refrigerator. It was then 
topped on a roto-vac at 70.degree. C. to yield 5.7 grams of a viscous oil 
containing 
3-[5-(t-butyl)-3-isoxazolyl]-1-methyl-1-(2,2-dimethoxyethyl)urea. The oil 
crystallized on cooling, and the crystals were recrystallized from 
ethylether/hexane solution with refrigeration. The crystals were removed 
by suction filtration and air dried to yield 5.2 grams of white crystals 
of 3-[5-t-butylisoxazol-3-yl]-1-methyl-1-(2,2-dimethoxyethyl)urea. M.P. 
80.degree.-84.degree. C., IR spectra (mull.) bands at 3260, 1670, 1600, 
and 1530 cm.sup.-1, MS ion at m/e at 285. NMR (CDCl.sub.3) 9.11.delta. 
(singlet, 1H); 6.61.delta. (singlet, 1H); 4.52.delta. (triplet, 1H); 
3.42.delta. (singlet 8H); 3.50.delta. (doublet, 8H); 3.13.delta. (singlet 
3H); 1.30.delta. (singlet, 9H). 
EXAMPLE 2 
Preparation of 
3-(5-t-butyl-isoxazol-3-yl)-1-methyl-1-(1,3-dioxolan-2-ylmethyl)urea 
14.19 grams (0.085 mole) of 5-t-butyl-isoxazol-3-yl isocyanate prepared as 
described in paragraph (a) of Example 1, was slurried in a flask with 100 
milliliters of toluene. To the slurry was added, dropwise, with stirring, 
over a 5-minute period at 24.degree. C. (0.085 mole) of 
N-(1,3-dioxolan-2-ylmethyl)-methylamine in 10 milliliters of toluene. 
(Note: 19.4 grams of N-(1,3-dioxolane-2-ylmethyl)methylamine was used 
which due to inert impurities, corresponds to 10 grams of pure material.) 
The reaction mixture was slowly heated to a temperature of 90.degree. C., 
at which temperature a clear, pale yellow solution was obtained. Heating 
was discontinued and the solution was allowed to cool overnight with 
continuous stirring. The reaction mixture was then cooled in ice bath and 
the white solid precipitate (presumed to be the inert "impurities" 
contained in the N-(1,3-dioxalan-2-ylmethyl)-methylamine) was removed by 
filtration. The mother liquor was concentrated by evaporation giving 15.3 
grams of pale yellow oil. Removal of solvent yielded a white crystalline 
solid, melting at 127.5.degree.-131.degree. C., and identified by IR and 
NMR spectroscopy as the desired product, 
3-[5-(t-butyl)-3-isoxazolyl]-1-methyl-1-(1,3-dioxolan-2-ylmethyl)urea. 
The mode of synthesis of specific compounds of this invention have been 
illustrated by the foregoing Examples; but, it is to be understood that 
any compound contemplated within the scope of this invention may be 
prepared by those skilled in the art simply by varying the choice of 
starting materials and using the illustrated techniques or other suitable 
techniques. 
The compounds of this invention have been found effective in regulating the 
growth of a variety of undesirable plants, i.e., weeds, when applied in an 
herbicidally effective amount to the growth medium prior to emergence of 
the weeds or to the weeds subsequent to emergence from the growth medium. 
The term "herbicidally effective amount" is that amount of compound or 
mixture of compounds required to so injure or damage weeds such that the 
weeds are incapable of recovering following application. The quantity of a 
particular compound or mixture of compounds applied in order to exhibit a 
satisfactory herbicidal effect may vary over a wide range and depends on a 
variety of factors such as, for example, hardiness of a particular weed 
species, extent of weed infestation, climatic conditions, soil conditions, 
method of application, and the like. Typically, as little as 0.2 or less 
pound per acre to 10 or more pounds per acre of compound or mixtures of 
compounds may be required. Of course, the efficacy of a particular 
compound against a particular weed species may readily be determined by 
relatively straightforward laboratory or field testing in a manner well 
known to the art. 
The compounds of this invention may be used as such or in formulation with 
agronomically acceptable adjuvants, inert carriers, other herbicides, or 
other commonly used agricultural compounds, for example, pesticides, 
stabilizers, safeners, fertilizers, and the like. The compounds of this 
invention, whether or not in formulation with other agronomically 
acceptable materials, are typically applied in the form of dusts, 
granules, wettable powders, solutions, suspension, aerosols, emulsions, 
dispersions or the like, in a manner well known to the art. When 
formulated with other typically used agronomically acceptable materials, 
the amount of compound or compounds of this invention present in the 
formulation may vary over a wide range, for example, from about 0.05 to 
about 95 percent by weight on weight of formulation. Typically, such 
formulations will contain from about 5 to about 75 percent by weight of 
compound or compounds of this invention. 
The compounds of this invention as exemplified by the compounds prepared in 
Examples 1 and 2, have been found effective in controlling a variety of 
broadleaf and grassy weeds when applied either preemergence or 
postemergence. The compounds prepared according to Examples 1 and 2 were 
tested for herbicidal activity against various weed species under 
controlled laboratory conditions of light, temperature, and humidity, 
using techniques known to the art. In preemergence evaluation, a solvent 
solution of the test compound is applied at the desired rate to the weed 
species prior to emergence from the growth medium whereas in postemergent 
evaluation, a solvent solution of the test compound is applied at the 
desired rate directly on the growing plant, the toxic effect of the 
compound being determined by visual inspection periodically after 
application. 
Each of the compounds prepared in Examples 1 and 2 were individually 
applied both preemergence and postemergence at an application rate of 10 
pounds per acre to common broadleaf and grassy weeds, namely teaweed (Sida 
spinosa), jimson weed (Datura stramonium), wild mustard (Brassica kaber), 
yellow nutsedge (Cyperus esculentus), yellow foxtail (Setaria glauca), 
large crabgrass (Digitaria sanguinalis), johnsongrass (Sorghum halepense), 
coffeeweed (Daubentonia punicea), velvetleaf (Abutilon theophrasti), tall 
morningglory (Ipomoea purpurea Roth), wild oats (Avena fatua), 
barnyardgrass (Echinochloa crusgalli), and cotton, var. DeltaPine 61 
(Gossypium hirsutum). 
Herbicidal efficacies were determined by visual inspection periodically 
after application and a Numerical Injury Rating assigned, based on a scale 
of 0 (or injury) to 10 (all plants dead). The following Table gives the 
Numerical Injury Ratings for the various weed species against which the 
compounds prepared in Examples 1 and 2 were tested. The Numerical Injury 
Ratings were determined twenty one (21) days after both preemergence and 
postemergence applications for the compound of Example 1 and twenty two 
(22) days after both preemergence and postemergence applications for the 
compound of Example 2. 
TABLE 
______________________________________ 
Preemergence and Postemergence Herbicidal Activities 
of the Compounds of Examples 1 and 2 
Compound 
Example 1 Example 2 
Emergence 
Weed Species Pre Post Pre Post 
______________________________________ 
Teaweed 10 10 10 10 
Jimsonweed 10 10 10 10 
Wild mustard 10 10 10 10 
Yellow nutsedge 
5 6 4 1 
Yellow foxtail 10 10 10 6 
Large crabgrass 
10 -- 10 -- 
Cotton -- 10 -- 10 
Johnsongrass 9 10 10 10 
Coffeeweed 10 10 10 10 
Tall morningglory 
10 10 10 9 
Wild oats 10 10 9 7 
Barnyardgrass 10 10 10 10 
Application Rate, 
10 10 10 10 
lb/A 
______________________________________