Compounds having the following structural formula ##STR1## wherein R is alkyl which are useful as herbicides.

BACKGROUND OF THE INVENTION 
The compounds 1-hydroxy-2-isovaleryl-4,4,6,6-tetramethyl 
cyclohexen-3,5-dione and 1-hydroxy-2-isobutyrl-4,4,6,6-tetramethyl 
cyclohexen-3,5-dione having the structural formulae 
##STR2## 
respectively have been isolated from the plant family Myrtaceae, plant 
genus Leptospermum and Xanthostemon and are described in the literature 
(R. O. Hellyer, Aust. J. Chem., 21, 2825 (1968) but no utility therein is 
taught. 
Also, the compound 1-hydroxy-2-acetyl-4,4,6,6-tetramethyl 
cyclohexen-3,5-dione having the structural formula 
##STR3## 
is known but no utility for the compound is taught (A. C. Jain and T. R. 
Seshadri, Proc. Indian Acad. Sci. 42A, 279-84 (1955)). 
DESCRIPTION OF THE INVENTION 
This invention relates to certain novel 
1-hydroxy-2-(alkylketo)-4,4,6,6-tetramethyl cyclohexen-3,5-diones as 
herbicides. The compounds of this invention have the following structural 
formula 
##STR4## 
wherein R is alkyl having 2 to 6 carbon atoms, except isopropyl and 
isobutyl, preferably 2 to 4 carbon atoms, except isopropyl and isobutyl. 
The compounds of this invention can have the following three structural 
formulae because of tautomerism: 
##STR5## 
wherein R is as defined. 
In the above description of the compounds of this invention, alkyl includes 
both straight chain and branched chain configurations, for example, ethyl, 
n-propyl, n-butyl, sec-butyl or tert-butyl. 
The compounds of this invention are active herbicides of a general type. 
That is, they are herbicidally effective against a wide range of plant 
species. The method of controlling undesired vegetation of the present 
invention comprises applying a herbicidally effective amount of the 
above-described compounds to the area where control is desired. 
The compounds of the present invention are prepared by the following 
general method. 
##STR6## 
wherein R is as defined. 
A method of synthesis is described in Organic Syntheses, Collective Vol. 
II, Ed. by A. H. Blatt, John Wiley and Sons, Inc., (1943), pages 522 and 
523, for the preparation of phloroacetophenone, i.e., the compound where R 
is methyl. Compounds where R is alkyl having 2 to 6 carbon atoms are novel 
intermediates and can be correspondingly prepared by substituting the 
appropriate RCN for CH.sub.3 CN. 
##STR7## 
wherein R is as defined. 
Generally, six moles of iodomethane is added very slowly to a solution 
containing one mole ketone and six moles sodium ethoxide in methanol. The 
reaction mixture is heated to reflux for 3-4 hours followed by removal of 
excess iodomethane and methanol by distillation. Next, the concentrated 
product is diluted with water and acidified with hydrochloric acid 
followed by extraction with ether. The ethereal solution is washed with 
sodium sulfite and then water, followed by drying over sodium sulfate and 
evaporation of the ether to yield the desired product. 
Similarly effective as herbicides are mono- and divalent metal salts of the 
above-described compounds of this invention. The monovalent metal salts 
have the structural formula 
##STR8## 
and the divalent metal salts having the structural formula wherein R is 
as defined. 
The monovalent metal ion (M.sup.+) can be any Group I metal, preferably 
potassium or sodium. The divalent metal ion (M.sup.++) can be any Group 
II-A metal, iron or copper, preferably magnesium, calcium, iron or copper. 
The monovalent metal salts are easily prepared by reacting a mole of a 
compound of this invention as described above with about a mole of a 
monovalent metal hydroxide such as potassium hydroxide or sodium 
hydroxide. 
The divalent metal salts are correspondingly prepared by reacting two moles 
of a compound of this invention with about a mole of divalent metal 
hydroxide such as calcium hydroxide or magnesium hydroxide. 
For the preparation of both mono- and divalent metal salts of the compounds 
of this invention, the above reaction can be carried out in an organic 
solvent for the compound and the metal hydroxide, followed by evaporation 
of the solvent and water at reduced pressures. Preferred solvents are 
methanol, ethanol and acetone, most preferably methanol. 
Also, similarly effective as herbicides are amine salts of the 
above-described compounds which have the structural formula 
##STR9## 
wherein R is as defined and R.sup.1, R.sup.2 and R.sup.3 can be hydrogen 
or alkyl having 1 to 6 carbon atoms. 
These amines salts are prepared by reacting a mole of the amine with a mole 
of the compound of the invention. Preferably the reaction is carried out 
in a solvent such as toluene without heating. 
Preparation of compounds of this invention is illustrated by the following 
example.

EXAMPLE I 
1-Hydroxy-2-Acetyl-4,4,6,6-Tetramethyl Cyclohexen-3,5-Diones 
##STR10## 
The example teaches a method of preparation for the above named compound. 
First 190.3 grams (1.34 moles) of iodomethane is added dropwise to a 
solution of 45 grams (0.27 mole) of 2,4,6-trihydroxy acetophenone 
(phloroacetophenone), 180 milliliters of methanol and 425 grams (1.98 
moles) of a 25% sodium methoxide methanol solution which is maintained at 
5.degree.-10.degree. C. The reaction mixture is heated for 3.5 hours and 
then concentrated at atmospheric pressure by distillation of iodomethane 
and methanol. Two hundred milliliters of water is added and the mixture is 
acidified with 5N hydrochloric acid and extracted with ether. The etheral 
solution is washed with 5% sodium sulfite and then water, followed by 
drying over sodium sulfate and evaporation of the ether. In this manner, 
50 grams (83%) of 1-hydroxy-2-acetyl-4,4,6,6-tetramethyl 
cyclohexen-3,5-diones is prepared which has been confirmed by instrumental 
analysis. 
The following is a table of certain selected compounds that were prepared 
according to the procedures described herein. Compound numbers are 
assigned to each compound and are used throughout the remainder of the 
specification. 
TABLE I 
______________________________________ 
##STR11## 
Compound 
Number R n.sub.D.sup.30 & m.p. 
______________________________________ 
1 isobutyl 1.4791 
2* methyl 37.degree.-40.degree. C. 
3 propyl Oily solid 
4 ethyl 1.4890 
______________________________________ 
*Prepared in Example I 
HERBICIDAL SCREENING TESTS 
As previously mentioned, the herein described compounds produced in the 
above-described manner are phytotoxic compounds which are useful and 
valuable in controlling various plant species. Selected compounds of this 
invention are tested as herbicides in the following manner. 
Pre-emergence herbicide test. 
On the day preceding treatment, seeds of seven different weed species are 
planted in individual rows using one species per row across the width of 
the flat. The seeds used are hairy crabgrass (Digitaris sanguinalis), 
yellow foxtail (Setaria glauca), watergrass (Echinochloa crusgalli), 
California red oat (Avena sativa), redroot pigweed (Amaranthus 
retroflexus), Indian mustard (Brassica juncea) and curly dock (Rumex 
crispus). Ample seeds are planted to give about 20 to 50 seedlings per 
row, after emergence, depending upon the size of the plants. The flats are 
watered after planting. Using an analytical balance, 20 milligrams of the 
compound to be tested was weighed out on a piece of glassine weighing 
paper. The paper and compound were placed in a 30 milliliter wide-mouth 
bottle and 3 milliliters of acetone containing 1% polyoxyethylene sorbitan 
monolaurate emulsifier was added to dissolve the compound. If the material 
was not soluble in acetone, another solvent such as water, alcohol or 
dimethylformamide (DMF) was used instead. When DMF was used, only 0.5 
milliliters or less was used to dissolve the compound and then another 
solvent was used to make the volume up to 3 milliliters. The 3 milliliter 
solution was sprayed uniformly on the soil contained in a small flat 7 
inches long, 5 inches wide and 2.75 inches deep, one day after planting 
weed seeds in the flat of soil. A No. 152 DeVilbiss atomizer was used to 
apply the spray using compressed air at a pressure of 5 lb/sq. inch. The 
rate of application was 8 lb/acre and the spray volume was 143 
gallon/acre. 
After treatment, the flats were placed in the greenhouse at a temperature 
of 70.degree. to 85.degree. F. and watered by sprinkling. Two weeks after 
treatment the degree of injury or control was determined by comparison 
with untreated check plants of the same age. The injury rating from 0 to 
100% was recorded for each species as percent control with 0% representing 
no injury and 100% representing complete control. 
Post-emergence herbicide test. 
Seeds of six plant species, including hairy crabgrass, watergrass, red oat, 
mustard, curly dock and pinto beans (Phaseolus vulgaris) were planted in 
the flats as described above for pre-emergence screening. The flats were 
placed in the greenhouse at 70.degree. to 85.degree. F. and watered daily 
with a sprinkler. About 10 to 14 days after planting, when the primary 
leaves of the bean plants were almost fully expanded and the first 
trifoliate leaves were just starting to form, the plants were sprayed. The 
spray was prepared by weighing out 20 milligrams of the test compound, 
dissolving it in 2.5 milliliters of acetone containing 1% polyoxyethylene 
sorbitan monolaurate and then adding 2.5 milliliters of water. The 
solution was sprayed on the foliage using a No. 152 DeVilbiss atomizer at 
an air pressure of 5 lb/sq. inch. The spray concentration was 0.2% and the 
rate is 8 lb/acre. The spray volume was 238 gallon/acre. 
The injury rating is from 0 to 100% as described above for the 
pre-emergence herbicide screening test. 
The results of these tests are shown in the following Table II. 
TABLE II 
______________________________________ 
Compound Pre-emergence Post-emergence 
Number Control Control 
______________________________________ 
1 86 98 
2 53 82 
3 27 68 
4 17 64 
______________________________________ 
The compounds of the present invention are used as pre-emergence or 
post-emergence herbicides and are applied in a variety of ways at various 
concentrations. In practice, the compounds herein defined are formulated 
into herbicidal compositions, by admixture, in herbicidally effective 
amounts, with the adjuvants and carriers normally employed for 
facilitating the dispersion of active ingredients for agricultural 
applications, recognizing the fact that the formulation and mode of 
application of a toxicant may affect the activity of the materials in a 
given application. Thus, these active herbicidal compounds may be 
formulated as granules of relatively large particle size, as wettable 
powders, as emulsifiable concentrates, as powdery dusts, as solutions or 
as any of several other known types of formulations, depending upon the 
desired mode of application. Preferred formulations for both pre- and 
post-emergence herbicidal applications are wettable powders, emulsifiable 
concentrates and granules. These formulations may contain as little as 
about 0.5% to as much as about 95% or more by weight of active ingredient. 
A herbicidally effective amount depends upon the nature of the seeds or 
plants to be controlled and the rate of application varies from about 0.05 
to approximately 25 pounds per acre, preferably from about 0.1 to 10 
pounds per acre. 
Wettable powders are in the form of finely divided particles which disperse 
readily in water or other dispersant. The wettable powder is ultimately 
applied to the soil either as a dry dust or as a dispersion in water or 
other liquid. Typical carriers for wettable powders include fuller's 
earth, kaolin clays, silicas and other readily wet organic or inorganic 
diluents. Wettable powders normally are prepared to contain about 5% to 
about 95% of the active ingredient by weight and usually also contain a 
small amount of wetting, dispersing or emulsifying agent to facilitate 
wetting and dispersion. 
Emulsifiable concentrates are homogeneous liquid compositions which are 
dispersible in water or other dispersant, and may consist entirely of the 
active compound with a liquid or solid emulsifying agent, or may also 
contain a liquid carrier, such as xylene, heavy aromatic naphthal, 
isophorone and other non-volatile organic solvents. For herbicidal 
application, these concentrates are dispersed in water or other liquid 
carrier and normally applied as a spray to the area to be treated. The 
percentage by weight of the essential active ingredient may varying 
according to the manner in which the composition is to be applied, but in 
general comprises about 0.5% to 95% of active ingredient by weight of the 
herbicidal composition. 
Granular formulations, wherein the toxicant is carried on relatively coarse 
particles, are usually applied without dilution to the area in which 
suppression of vegetation is desired. Typical carriers for granular 
formulations include sand, fuller's earth, bentonite clays, vermiculite, 
perlite and other organic or inorganic materials which absorb or which may 
be coated with the toxicant. Granular formulations normally are prepared 
to contain about 5% to about 25% of active ingredient and may also contain 
small amounts of other ingredients which may include surface-active agents 
such as wetting agents, dispersing agents or emulsifiers; oils such as 
heavy aromatic naphthas, kerosene or other pertroleum fractions, or 
vegetable oils; and/or stickers such as destrins, glue or synthetic 
resins. 
Typical wetting, dispersing or emulsifying agents used in agricultural 
formulations include, for example, the alkyl and alkylaryl sulfonates and 
sulfates and their sodium salts; polyhydric alcohols; and other types of 
surface-active agents, many of which are available in commerce. The 
surface-active agent, when used, normally comprises from 0.1% to 15% by 
weight of the herbicidal composition. 
Dusts, which are free-flowing admixtures of the active ingredient with 
finely divided solids such as talc, clays, flours, and other organic and 
inorganic solids which act as dispersants and carriers for the toxicant, 
are useful formulations for soil-incorporating applications. 
Pastes, which are homogeneous suspensions of a finely divided solid 
toxicant in a liquid carrier such as water or oil, are employed for 
specific purposes. These formulations normally contain about 5% to about 
95% of active ingredient by weight, and may also contain small amounts of 
a wetting, dispersing or emulsifying agent to facilitate dispersion. For 
application, the pastes are normally diluted and applied as a spray to the 
area to be affected. 
Other useful formulations for herbicidal applications include simple 
solutions of the active ingredient in a dispersant in which it is 
completely soluble at the desired concentration, such as acetone, 
alkylated naphthalenes, xylene or other organic solvents. Pressurized 
sprays, typically aerosols, wherein the active ingredient is dispersed in 
finely-divided form as a result of vaporization of a low boiling 
dispersant solvent carrier, such as the Freons, may also be used. 
The phytotoxic compositions of this invention are applied to the plants in 
the conventional manner. Thus, the dust and liquid compositions can be 
applied to the plant by the use of power-dusters, boom and hand sprayers 
and spray dusters. The compositions can also be applied from airplanes as 
a dust or a spray because they are effective in very low dosages. In order 
to modify or control growth of germinating seeds or emerging seedlings, as 
a typical example, the dust and liquid compositions are applied to the 
soil according to convention methods and are distributed in the soil to a 
depth of at least 1/2 inch below the soil surface. It is not necessary 
that the phytotoxic compositions be admixed with the soil particles since 
these compositions can also be applied merely by spraying or sprinkling 
the surface of the soil. The phytotoxic compositions of this invention can 
also be applied by addition to irrigation water supplied to the field to 
be treated. This method of application permits the penetration of the 
compositions into the soil as the water is absorbed therein. Dust 
compositions, granular compositions or liquid formulations applied to the 
surface of the soil can be distributed below the surface of the soil by 
conventional means such as discing, dragging or mixing operations. 
The phytotoxic compositions of this invention can also contain other 
additaments, for example, fertilizers, pesticides and the like, used as 
adjuvant or in combination with any of the above-described adjuvants. 
Other phytotoxic compounds useful in combination with the above-described 
compounds include, for example, 2,4-dichlorophenoxyacetic acids, 
2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and 
the salts, esters and amides thereof; triazine derivatives, such as 
2,4-bis(3-methoxypropylamino)-6-methylthio-s-triazine, 
2-chloro-4-ethylamino-6-isopropylamino-s-triazine, and 
2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine; urea 
derivatives, such as 3-(3,4-dichlorophenyl)-1,1-dimethyl urea and 
3-(p-chlorophenyl)-1,1-dimethyl urea; and acetamides such as 
N,N-diallyl-.alpha.-chloroacetamide, and the like; benzoic acids such as 
3-amino-2,5-dichlorobenzoic; thiocarbamates, such as S-propyl 
dipropylthiocarbamate, S-ethyl-dipropylthiocarbamate, S-ethyl 
cyclohexylethyl thiocarbamate, S-ethyl hexahydro-1H-azepine-1-carbothioate 
and the like; 4-(methylsulfonyl)-2,6-dinitro-N,N-substituted anilines, 
such as 4-(methylsulfonyl)-2,6-dinitro-N,N-substituted anilines, such as 
4-trifluoromethyl-2,6-dinitro-N,N-di-n-propyl aniline and 
4-trifluoromethyl-2,6-dinitro-N-ethyl-N-n-butyl aniline. Fertilizers 
useful in combination with the active ingredients include, for example, 
ammonium nitrate, urea and superphosphate. Other useful additaments 
include materials in which plant organisms take root and grow such as 
compost, manure, humus, sand and the like.