CA1148957A

CA1148957A - Herbicidally active 1,3,4-thiadiazole derivatives

Info

Publication number: CA1148957A
Application number: CA000095768A
Authority: CA
Inventors: Tony Cebalo
Original assignee: Air Products and Chemicals Inc
Current assignee: Air Products and Chemicals Inc
Priority date: 1969-10-17
Filing date: 1970-10-16
Publication date: 1983-06-28
Also published as: RO64525A; HU162349B; GB1284669A; CH530756A; ES384568A1; SE369907B; DE2050979A1; IE35302B1; DE2050979C2; BE757655A; IE35302L; IL35459A0; NL7015249A; FR2066127A5; JPS553323B1; IL35459A; MY7500251A

Abstract

ABSTRACT OF THE INVENTION

Novel thiadiazole compounds have the general structure:

Description

'i~5..~3~

The invention pertains to thiadiazoles and derivatives thereof which have utility as agricultural pesticides. The thiadiazoles may be represented most broadly, as having the structure:

RlR2NS02 ~ NR R

wherein Rl is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, and lower alkoxy, R2 is Rl or a lower alkoxy radical, except that Rl and R2 cannot both be hydrogen, R3 is hydrogen or a lower acyclic hydrocarbon radical, R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical, and, R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical or a substituted or un-substituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, or lower alkoxy, except that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical.

. . ~ :, . ., . . ~, .

~B~'7 The terms "lower acyclic hydrocarbon radical", lower cycloalkyl radical", and "lower alkoxy radical" are intended to mean such radicals containing up to seven carbon atoms.
It is to be understood that in Structure (I) above, where R3 is hydrogen, it may exist in the tautomeric form:
] ~ ~ a H

RlR2NS2 ~ S ~ _ NCONR4R5 where Rl, R2, R4, and R5 have the designations hereinbefore set forth. Therefore, in compositions of the invention where R3 is hydrogen, the above tautomeric structure is always implied to exist.
Y 1' R2, R3, R4, and R5 will have the same meaning throughout the entirety of the specification and claims.
The compounds show excellent activity as agricultural pesticides, particularly as herbicides, for controlling a broad spectrum of unwanted and undesirable weeks and plants.
Preferred Embodiments of the Invention Methods of Synthesis Generally, the compounds of the present invention may be prepared by one or more of the synthesis routes set forth below. The type of product desired will determine the particular synthesis route to be employed.

'"`

8~7 HN N HN- N
CH3COC~ 3 (II) S ~ S ~ NH 3 (or) CH3COOH S~ ~ NCOCH3 l C12 HN _ N ~ ~ 13 NCONR4R5 ClSO2 NCOCH3 C12 1 RlR2NH

(VII) I l R3 N -N R
ClSO2 ~ ~ CONR4 5 1 2 2 NCOCH3 1 RlR2NH ¦ HCl N N N N (V~

~ 2 2 ~ S ~ 4 5 RlR2NSO2 ~ ~ NHR3 RlR2N602 ~ ~ NHCONR4R5 (i) KOH RlR2NSO2 ~ ~ NCONR4R5 S(ii) R3X

NaOH/I2 / - R
(I) > ~ _ ~ . ~¦ ~ 13 t S S N3R3 / - 3 -5 ~ i ~ NCONR4 (VII) 8~357 The designations for Rl through R5 have been pre-viously described and the method of synthesis of any of the above-described compounds is dependent upon the desired compound.
Generally, the compound corresponding to formula (I) are known; however, others are prepared by standard methods. The 5-acetamido-1,3,4-thiadiazoles (II) utilized are prepared by known methods from (I) and the corresponding sulfonyl chlorides (III) are also prepared by known methods.
A particularly useful method is that of Petrow et al. (J.Chem.
Soc. 1508, 1958). The sulfonamides (IV) are prepared by the reaction of the sulfonyl chlorides with primary or secondary amines in aqueous or non-aqueous solutions at temperatures of 0-60C, preferably in the range 0-10C. For non-aqueous reactions inert solvents such as benzene, halogenated hydro-carbons, tetrahydrofuran and the like can be used. The 2-amino-5-sulfonamido-1,3,4-thiadiazoles (V) are obtained by the treatment of compounds (IV) with concentrated hydro-chloric acid according to the method of Petrow et al.
(loc. cit.).
A number of 2-ureido-1,3,4-thiadiazole sulfonyl chLorides (VII) and 2-ureido-1,3,4-thiadiazole sulfonamides (VIII) are prepared by methods similar to those employed to produce compounds (III) and (IV).
Other ureido compounds may be derived from compound (V) according to a variety of methods which are used for the preparation of such compounds and which are well docu~ented in the chemical litera~re. For ex~le, c~x~nds of Structure ~ may .
,..

8~S7 be reacted with isocyanates in an inert solvent such as benzene, dimethylformamide, ethyl acetate and the like. A catalyst such as triethylamine may be employed for this reaction.

52 ~ ~1 ~ + ~CO ~ ~R2~S2 -~ ~

Another reaction which may be employed is that in which a carbamoyl chloride is reacted with an amine in the presence of an acid fixing compound such as sodium carbonate, triethylamlne, pyridine and the like. Another variation of this reaction is the reaction of a metal derivative of an amine with a carbamoyl chloride. Inert solvents such as benzene, tetrahydrofuran, dimethyl formamide, dioxane and the like may be used to carry out the above reaction.
N _ N

2 ~ ClOONR4~N N

S RlS2~02 ~S~/ ~;E~R5 RlR2NS2~ r~o~4l X = Na, K or Li :- . - '' A further reaction which may be employed is that in which NN'-carbonyldiimidazole is reacted with an aminothiadiazole to give an intermediate isocyanate which is then further reacted with an amine to produce the desired product.
Q ~ R, O~ NSO~ ~JUL ~ S 2J~5/L ~ ¦

~50 ~ ~ ~HCO~ R~RSNH ~ 50 ~ ~ ~CO + H~F ¦

Phosgene may also be reacted with an amine to give a carbamoyl chloride which is then further reacted with a primary or secondary amine to produce the desired urea product. This reaction may be carried out in the presence of a base, e.g., tertiary amine, and/or a catalyst such as boron trifluride-ether complex. These reactions can also be carried out in inert solvents such as aromatic hydrocarbons, dimethyl formamide, tetrahydrofuran and the like.

~ ~ N 50~ 3 ~ co 1~ / 5 ~s~

' ¦ R~RSIV~

~so,~ rJcO~ qR5 The ureas of the invention which correspond to the generic formula (IX) will form metal or am-monium salts (substituted or unsubstituted) corres-ponding to structure (X). For polyvalent metals, these salts are chelate in character. The alkali metal and ammonium salts also possess the highly desirable property, for agricultural applications, of being water soluble. Furthermore, alkali metal salts are found to react with reactive halogen compounds, e.g., alkyl halides, to produce derivatives as shown in (XI) and (XII) below:

N

lR2N5 ~ l ~ HCONR4R5 (IX) ' N - N ~

Y = metal or ammonium radical ~.
n = equivalence of Y

N N

~`~ ~ N50 ~ S ~ 1CONR4 N - Nl ~

N5 2 5 ~ NOONR4R5 (XII) 8~57 The following examples are illustrative of the invention and are not intended to limit the scope thereof.
~thesis of Intermediates Example 1 __ To a well stirred mixture containing 231 gms of polyphosphoric acid and 488 gms of acetic acid and heated to 100C was added 300 gms of 2-amino-5-mercapto-1,3,4-thiadiazole. Upon complete addition of the thiadiazole, the mixture was stirred for an additional l hour at 120C.
The mixture was cooled to 60C and poured into ice water to provide a solid residue which was subsequently separated by filtering. The residue was dissolved in 10% sodium hydroxide (the small amount of insolubles being removed by filtering) and the solution being adjusted to pH of 1 with 6N hydrochloric acid. The solid product was identified to be 2-acetamido-5-mercapto-1,3,4-thiadiazole having a melting point of 293 - 294C.
Example 2 One hundred fifty grams of 2-acetamido-5-mércapto-1,3,4-thiadiazole was suspended in 3.5 litres of 70% acetic acid and cooled to a temperature of 0-5C. A stream of chlorine gas was slowly bubbled through the cooled mixture at the above temperature for about 2 hours with vigorous stirring. The solids were separated by filtering, washed with ice water and air dried. The solid product was identi-fied to be 2-acetamido-S-chlorosulfonyl-1,3,4-thiadiazole having a melting point of 237-239C.
Example 3 Two hundred fifty mls of a 40% solution of aqueous dimethylamine was added to 168.5gms of 2-acetamido-5-chlorosulfonyl-1,3,4-thiadiazole while maintaining the termpature below 20C. After stirring the mixture for about 4 hours, the mixture was acidified with 6N hydrochloric acid, the solids separated by filtration and washed thoroughly with water. The solid product was identified to be 2-acetamido-5-NN-dimethylsulfonamido-1,3,4-thiadiazole having a melting point of 258 - 260C.
Example 4 ' A mixture containing 181.6 gms of 2-acetamido-1,3,4-thiadiazole-5-NN-dimethylsulfonamide and 1000 mls of concentrated hydrochloric acid was refluxed for about

3 1/2 hours. The mixture was cooled to room temperature, filtered and the filtrate concentrated to dryness under vacuum. The solid residue was admixed with 200 mls of 10%
aqueous sodium carbonate and filtered. The resulting solid residue was identified to be 2-amino-1,3,4-thiadiazole-5-NN-dimethylsulfonamide and having a melting point of 184-186C.
~xample 5 A mixture containing 8.0 gms of 2-amino-5-mercapto-1,3,4-thiadiazole, 3.4 gms of methylisocyanate and 150 mls of NN-dimethylformamide was heated to 50C for about 1 hour.
The reaction mixture was concentrated under vacuum and ice water subsequently added to the concentrate. The solid residue was separated by filtration and identified to be l-methyl-3-(S-mercapto-1,3,4-thiadiazole-2-yl)urea having a melting point of 234C.

' :

~ ~ ~ 8',~7 Example 6 Sixty gms of l-methyl-3-(5-mercapto-1,3,4-thiadiazole-2-yl) urea was suspended in 1.32 litres of 70% acetic acid, the mixture being formed in a flask equipped with a mechanical stirring means. The mixture was cooled to about 5C and chlorine gas slowly bubbled through for about 45 minutes while maintaining the 5C
temperature. The resulting solids were separated by filtration, washed with water and air dried. The product was identified to be l-methyl-3-(5-chlorosulfonyl-1,3,4-thiadiazole-2-yl)urea having a melting point of 141C.
Synthesis of Final Products Example 7 Twenty gms of l-methyl-3-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea was dissolved, with stirring, in 250 mls of a 40% aqueous solution of methylamine while maintaining the temperature of the reaction from about 5 - 7C. After stirring for an additional 1-1/2 hours, the mixture was acidified to pH 1 with 6N hydrochloric acid, the solids separated by filtration and subsequently washed with water.
The final product was identified to be l-methyl-3-(5-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 232 - 233C.
Example 8 A mixture containing 4.1 gms of 2-amino-1,3,4-thiadiazole-5-NN-dimethylsulfonamide and 1.3 gms of methylisocyanate was refluxed in anhydrous benzene for 3 hours. The :;
,~
~ ~ , .

~ 5 ~

mixture was cooled to 10C, the solid product separated by filtration and subsequently crystallized from ethanol.
The final product was identified to be l-methyl-3-(5-NN-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 223- 23~C.
Example 9 A mixture containing 18.0gms of 2-amino-1,3,4-thiadiazole-5-(N-methyl-N-butyl)sulfonamide, 5.4 gms of methylisocyanate and 300 mls of anhydrous dimethylformamide was heated to and maintained at 50C for about 1 hours.
The dimethylformamide was removed under vacuum and the solid residue crystallized from solox. The final product was ldentified to be l-methyl-3-(5-N-butyl-N-methylsulfamoyl-l, 3,4-thiadiazol-2-yl)urea having a melting point of 192-Example 10 The procedure of Example 9 was substantially re-peated except that 13.8 gms of 2-amino-1,3,4-thiadiazole-5-butylsulfonamide, 4.3 gms of methylisocyanate and 250 mls of anhydrous dimethylformamide were employed. The final product was identified to be l-methyl-(5-N-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 186 - 187C.
Example 11 A mixture containing 28.2 gms of 2-amino-1,3,4-thiadiazole-5-NN-dimethylsulfonamide, and 12.5 gms cyclo-propylisocyanate and 400 nls of anhydrous dimethylform~de was heated to and 7' maintained at 50C for about 1 hour. The dimethylform-amide was removed under vacuum, leaving a solid residue which was crystallized from methanol. The final product was identified to be l-cyclopropyl-3-(5-NN-dimethyl-sulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 216C.
Example 12 A mixture containing 20 gms of 2-amino-5-morpholino-sulfonyl-1,3,4-thiadiazole, 6.0 gms of methylisocyanate and 200 mls of anhydrous dimethylformamide was heated to and maintained at 50C for about 1 hour. The dimethylformamide was removed under vacuum and the solid residue crystallized from a benezenemethanol mixture. The resulting product was identified to be l-methyl-3-(5-morpholinosulfonyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 245-246C.
~xample 13 To amixture containing 28.2 gms of 2-amino-1,3,

4-thiadiazole-5-NN-dimethylsulfonamide and 18.4 gms of N
butyl-N-methyl carbamoyl chloride in 150 mls of anhydrous tetrahydrofuran, was added in small portions, 4.7 gms of sodium hydride. The reaction mixture was stirred for 1 1/2 hours, water added and the mixture subsequently extracted with ethyl acetate. The ethyl acetate solution was dried over anhydrous sodium sulfate and concentrated under vacuum. The solid residue was crystallized from ethyl acetate. The final product was identified to be l-butyl-l-methyl-3-(5-NN-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 163 - 165C.

~' .

., ., . : .

E ~mple 14 To a mixture containing 100 mls of methanol, and 10 gms 1-methyl-3-(5-NNdimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea was added 2.4 gms of potassium hydroxide and 5.4 gms of methyl iodide, the entire mixture being refluxed for 30 minutes. The solids were separated by filtration and the filtrate concentrated under vacuum to provide a solid residue. The residue was recrystallized from methanol.
The final product was identified to be 1,3-dimethyl-3-(5-NN-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea having a melting point of 209-212C.
Example 15 To a mixture of 6 gms of NN'-carbonyldiimidazole in dry tetrahydrofuran, under an atmosphere of nitrogen, was added 3.5 gms of 2-amino-1,3,4-thiadiazole-5-NN-dimethyl-sulfonamide. The mixture was stirred at room temperature for 30 minutes and subsequently refluxed for about 15 minutes. The reaction mixture was cooled to room tempera-ture and 5.6 gms of triethylamine and 5.4 gms of N,0-dim-ethylhydroxylamine hydrochloride were added. The resulting mixture was stirred for about 15 minutes after which the mixture was poured into ice water. The solid residue was separated by filtering and theresidue subsequently crystallized from methanol. The final product was identi-fied to be l-methyl-l-methoxy-3-(5-NN-dimethylsulfamoyl-1,3,4,-thiadiazol-2-yl)urea having a melting point of 147 - 149C.
Additional compounds of the invention were pre-pared in accordance with the procedures set forth above.

~ ~*~ ~ 7 Example Rl R2 Ra R4 R5 Melting Point, 17 CH3 CH3 H ~H~ CH3 187-189 18 CH2=CHCH2 H H H GH3 166-168 19 C3H7 C3~ H H CH3 158-159 E~le 20 To a stirred suspension of 80 gms of 5-methylamino-2-mercapto-1,3,4-thiadiazole in 300 mls of methanol was added, in small portions, 26 gms of sodium hydroxide. The stirring was continued until a complete solution was obtained (a small amount of insoluble material being removed by filtration).
Iodine (66.4 gms) dissolved in 350 mls of methanol was next added drop-wise to the above stirred solution. A yellow precipitate began to separate after approximately half of the iodine solution had been added. After complete addition of the iodine solution the solids were filtered off and washed with a little methanol to give the desired di-5-(methylamino-1,3,4-thiadiazolyl) disulfide (XIII, R3= CH3) having a melting point of 202-204C.
Example 21 A mixture containing 4 gms of di-5-(2-methyl-amino-1,3,4-thiadiazolyl) disulfide, 1.6 gms of methyliso-cyanate, and 20 mls of NN-dimethylformamide was heated at 100C for 1.75 hours. Water was next added to the reaction mix-ture until a precipitate appeared. Thetotal solids which pre-cipitated on further cooling were removed by filtration and were washed thoroughly with water.

...

.. . . . .
.

o57 The resulting product was identified to be die-5-[1, 3-dimethyl-3-(1,3,4-thiadiazol-2-yl)urea]disulfide (XIV, R4= H; ~3= R5 = CH3) having a meIting point of 219-221C.
Example 22 Four gms of di-5-[1,3-dimethyl-3-(1,3,4-thiadiazol-2-yl)urea] disulfide was suspended in 120 mls of 70% acetic acid, the mixture being formed in a flask with mechanical stirring means. The mixture was cooled to about 10C and chlorine gas slowly bubbled through for 1 hour while maintaining a temperature range of 10-15C. After approximately 30 minutes, the reaction mixture became clear.
The reaction mixture was next diluted with water and ex-tracted with chIoroform. The chloroform solution was washed with water, dried (Na2SO4) and concentrated under vacuum to give the desired 1,3-dimethyl-3-(5-chlorosulfonyl-1,3,4-thiadiazole-2-yl)urea having a melting point of 9~-100C
(dec).
Example 23 To a stirred mixture containing 1.5 gms of 1,3-dimethyl-3-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea and ; 0.5 gms of dimethylhydroxylamine hydrochloride in 20 mls of tetrahydrofuran was added, dropwise, 1.0 gms of triethylamine ` in 5 mls of tetrahydrofuran and the reaction mixture stirred overnight at room temperature. The reaction mixture was next filtered and the filtrate concentrated under vacuum to a solid residue. This solid was dissolved in ethyl acetate, washed successively with dilute hydrochloric acid and water, dried (Na2SO4) and concentrated under vacuum.
The residual solid was crystallized from aqueous ~r i~ - 16 -~ 8~ ~ 7 methanol. The final product was identified to be 1,3-dimethyl-3~5-(N-methoxy-N-methyl)sulfamoyl-1,3,4-thiadiazol-2-yl]urea having a melting point of 190 - 192C.
The following additional compounds of the in-vention were prepared using the above procedures.
E~m,ple ~ R2 R3 , R,4 R5 ~llOting Point, ~4C( ~ )3 H H H 'CH3 247-249 2 ~X~
S CH3 CH2CH~ ~ H H CH3 156-158 26 H H H H CH3 245-247 (dec) 27ClCH2CH2 H H H CH3 197-199 28 CH3 ~ H H CH3 167-169 29C~CHC~ ~ H H H CH3 174-176 30C~CN CH3 CH3 H CH3 200-202 31C~CN C4Hg H H CH3 127-130 Biolog'ical Activity of Fin'al Products The herbicidal activity of products of the in-vention were tested in accordance with the procedure herein-after set forth. For pre-emergence testing the soil in which seeds were planted, was sprayed the same day with a solution containing the designated amount of product in a 50-100%
acetone-water mixture. Observations of activity were recorded twenty-one (21) to twenty-eight (28) days after planting and spraying. For post-emergence testing, the plants were sprayed with the same solution as described above about fourteen (14) days after planting of the seeds.
A vigor and kill rating was adopted to assess the phytotoxicant properties of the products. For both testing procedures a percent kill rating . - . ., , ~ - , ~ t~7 for each species of plants was obtained by comparing the stand of treated plantings with untreated control plants growing under similar conditions. A vigor rating of 1 to 5 was given to those plants not killed by chemical treatment and is defined as follows:
1. severe injury, plants will die.
2. moderate-to-severe injury, plants are not expected to recover from chemical treatment.
3. moderate injury, plants are expected to show various degrees of recovery from chemical treatment.
4. slight injury, plants will or have recovered and will resume normal growth.

5. no apparent injury The following tables show the pre- and post-emergence herbicidal activity of compounds of the invention.

.. .
,~

The evaluated plant species are identified below as to their corresponding Latin names:

Sugar Beets: Beta vulgaris Corn: Zea mays Oats: Avena sativa Clover: Melilotus indica Soybeans: Glycine max Cotton: Gossypium hirsutum Mustard: Brassica juncea Yellow Foxtail: Setaria lauca Barnyardgrass: Echinochloa crusgalli Crabgrass: Digitaria sanguinalis Buckwheat: Fagopyrum tataricum Morningglory: Ipomoca purpurca Pigweed: Amaranthus retroflexus Jimsonweed: Datura stramonium ~ .
i,. i,.
: . .

.~ ~ o o o o o o U~ o o o U~ o .~ o o o o ~o ~o ~o ~ ~ ~o ~ ~ o~ ~o u~
.... ,. . .,, . .. ,,.. . ., ., ., ., .. ... .... .....
;~ ~ 8~ 8 ~g o o o 8 8 o ~ ~8 ~o ~

_ .. ~ . ,. .................. . .. ...... .
, ~q ~ 8 8 g ~ 8 g g ~ 8 8 U. 8 8 8 : ~ ~ . ~ ~ ~ ~
~ ~ ~ ~ ~ ~ .
s~ U~ ~ .~ o o o o ~ o o, o o U~ o o o U~ o~ to ~.,, o o o ~i o o o~ ~. o o o~ o~ o o o~
~ :~ ~ ~

~n ~ o oo ooo oooo ooU~O
0~ ~ ~ ~0 o~

~ l 8~o ~ o ~ 8 ~o~8 8 o~ 8~ o~ 8 ~ ~ ~ ~ ~ ~L ~ ~
~ _ ~__ . _ rl d j_l O O O O O O O O i O O O O O O O O
? ~ ~.~ oo ~ o G 0~ ~ 1 ~0 00 ~
¢ ~ ~3 g! ~ ~ ~ ~
H ¦ ~ ~ ~ .~ 8 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~o . ~ ~( ~ ~ ~
I . ~ ~ oooo ooooooot~ oooo bj ~ OOO~ Ooooloooo oooo h ~; ~ ~1 ~1 ~1 ~1 ,~ 1 ~ ~1 ~1 ~1 ~ l Pl . ~ ~ `J
_ ~ O O O O O O O O O O O O O O O O
~ 1~; ,0~0000 o~O~ ~ ~ I
5! ~ ~1 ~ ~ ~ -) .
: ~ 8 ~ o o 8 ~ 8 ~
~ i ~ ~ ~
~- ~ ~ ~ ~ ~ ~
~ u~ ~ o o o o o o o o o o o u~ o o o u~
~ ~-rl OOO OOO00 OOOO~ O
t ~ t)i ~ 1 ~ ~ 1 5;!' .. ~ ~ ~ ~
~ ~ ~ ~ o ~ ~ ~ o ~ o ~ o .
~0~ 00 ~ ~ ~ __ .
_ ~ .
,~ - 20 -3~i'7 .~ _ ~ o o o c o o ~ .

:~ _ :, . . _. _ . . . . 1.., I

;~ ~ h O O O
- 8 8 ~~~ æ~ ~. _ ~
~ ~ ~, ~ ~ ~

~ 1~ 1~ 883 _ i~ 0 b ~1 Oo U~) ~ I ~
~ ,,~ ::~! oo~ ~, _ c~, . ~1 ~.~ o ~ o H ~ 0 1~i ~ /~ ~ ¦ ----~
~3 ~ ~ ~~ o ~0 0 C`~
~ - _ ~ ~ ~ _ _ .
: p~ ~ ~ 0 00 o ~ ~ U~ ~ ,0~ ,, ; _ ~ 0OO ~ ~ _ r :~:
~ ~5 ~ 8 ~ r _ _ ~ : ~ ~ O O O O O O O
'~ _ ~ ~ u) u~ ~ u~
~ ~ ~ 0 ~0~0 ~.' , _ _ _ _ _ ~
. ~ ~0 ~ C~ C~l C~ ~ ,, . ~,, ~ _ _ _ .~

~ 0~ . ... ~ ~ Ic~l c~

:~ :

~r~ 7 When utilized for herbicidal purposes, compounds of the invention may be formulated in a variety of ways and concentrations for application to the locus of desired vegetation control. It is recognized that the particular type and concentration of formulation, as well as the mode of application of the active ingredient, may govern its biological activity in a given application.
Compounds of the invention may be prepared as simple solutions of the active ingredient in an appropriate solvent in which it is completely soluble at the desired concentration. Such solvent systems include water, al-cohols, acetone, aqueous alcohol and acetone, and other organic solvents. These simple solutions may be further modified by the addition of various surfactants, emulsi-fying or dispersing agents, colorants, odorants, anti-foaming agents, other herbicides or herbicidal oils which supplement or synergize the activity of the herbicides of the invention, or other adjuvants for any given application where deemed desirable to impart a particular type or degree of plant responses.
Compounds of the invention may also be formulated in various types of formulations commonly recognized by those skilled in the art of agricultural or industrial chemicals. These formulations include, for example, compositions containing the active ingredient as granules of relatively large particle size, as powder dusts, as wettable powders, as emulsifiable concentrates or as a constituent part of any other known type of formulation commonly utilized by those skilled in the art. Such fora,ulations inlclude the adjuvants and carriers normally employed for facilitating the dispersion of active ingredientfor a~ricultral and ~; - 22 -.~ .~i..

industrial applications of phytotoxicants. These formula-tions may contain as little as 0,25% or more than 95% by wei.ght of the active ingredient.
Dust formulations are prepared by mixing the active ingredient with finely divided solids which act as dis-persants and carriers for the phytotoxicant in applying it to the locus of application for vegetation control~ Typical solids which may be utilized in preparing dust formulations of the active ingredients of the invention include talc, kieselguhr, finely divided clay, fullers' earth, or other common organic or inorganic soli~s. Solids utilized in preparing dust formulations of the active ingredient normally have a particle size of 50 microns or les~. The active ingredient of these dust formulations i8 present commonly from as little as 0.25% to as much as 30% or more ~ -by weight of the composition.
Granular formulations of the active ingredients are prepared by impregnating or adsorbing the toxicant on or into rleatively coarse particles of inert solids such as sand, attapulgite clay, gypsum, corn cobs or other in-organic or organic solids. The active ingredient of these granular formulations is commonly present from 1.0% to as much as 20. OV/D or more by weight of the composition.
Wettable powder formulations are solid compositions of matter wherein the active ingredient is absorbed or adsorbed in or on a sorptive carrier such as finely divided clay, talc, gypsum, lime, wood flour, fullers' earth, kieselguhr or the like. These formulations prefer-ably are made t~ contain 50% to 80% of active ''' ~ ' ~ .

~ i5~

ingredient. These wettable powder formulations commonly contain a small amount of a wetting, dispersing or emulsi-fying agent to facilitate dispersion in water or other liquid carrier utilized to distribute the phytotoxicant to the locus of desired vegetation control.
Emulsifiable concentrate formulations are homo-geneous liquid or paste compositions containing the active ingredient which will disperse in water or other liquid carrier to facilitate application of the phytotoxicant to the locus of desired vegetation control. Such emulsi-fiable concentrate formulations of the active ingredients may contain only the active ingredient with a liquid or solid emulsifying agent or may contain other relatively non-volatile organic solvents such as isophorone, dioxane, heavy aromatic naphthas, xylene, or dimethyl formamide.
The active ingredient in such formulations commonly com-prises 10.0% to 70.0% by weight of the phytotoxicant composition.
In place of the particular compositions employed to produce the products of the invention, other composi-tions and procedures may also be employed to produce products of the invention having substantially the same degree of biological activity.

~,

Claims

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

1. A thiadiazole having the formula:

[A]
wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being halo, hydroxy, cyano or lower alkoxy;

R2 is R1 or a lower alkoxy radical, with the proviso that R1 and R2 cannot both be hydrogen;

R3 is hydrogen or a lower acyclic hydrocarbon radical;

R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical; and R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being halo, hydroxy, cyano, or lower alkoxy, with the proviso that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical; or [B] a tautomer of [A], wherein R3 is hydrogen; or [C] a metal or ammonium salt of [A] wherein R3 is hydrogen;
but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:

when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;

when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;

when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;

when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;

when R1 and R2 are butyl, R3 and R4 are hydrogen and R5 is methyl;

when R1 and R2 are allyl, R3 and R5 are methyl and R4 is hydrogen;

when R1, R3 and R5 are methyl and R2 and R4 are hydro-gen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen.

2. A thiadiazole having the formula:

[A] wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, and lower alkoxy, R2 is R1 or a lower alkoxy radical, except that R1 and R2 cannot both be hydrogen, R3 is hydrogen or a lower acyclic hydrocarbon radical, R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical, and R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, or lower alkoxy, except that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical, or [B] a tautomer of [A] wherein R3 is hydrogen, but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:

when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;

when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;

when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;

when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;

when R1 and R2 are butyl, R3 and R4 are hydrogen and R5 is methyl;

when R1 and R2 are allyl, R3 and R5 are methyl and R4 is hydrogen;

when R1, R3 and R5 are methyl and R2 and R4 are hydro-gen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen.

3. A thiadiazole having the formula:

wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano and lower alkoxy, R2 is R1 or a lower alkoxy radical, except that R1 and R2 cannot both be hydrogen, R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical, R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, or lower alkoxy, except that R4 and R5 cannot both be hydrogen or a lower cycloalkyl ra-dical, Y is an alkali metal or ammonium radical, and n is the chemical equivalence of Y, but excluding the compounds wherein R1, R2, R4 and R5 have the following definitions:

when R1 is methyl; R2 and R4 are hydrogen and R5 is methyl; and when R1 and R2 are butyl, R4 is hydrogen and R5 is methyl.

4. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

5. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-butyl-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)-urea.

6. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

7. The thiadiazole according to claim 1, which is 1-cyclopropyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

8. The thiadiazole according to claim 1, which is 1-butyl-1-methyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

9. The thiadiazole according to claim 1, which is 1,3-dimethyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

10. The thiadiazole according to claim 1, which is 1-methyl-1-methoxy-3-(5-N,N-dimethylsulfamoyl-1,3,4-thia-diazol-2-yl)urea.

11. The thiadiazole according to claim 1, which is 1-n-butyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)-urea.

12. The thiadiazole according to claim 1, which is 1,1-dimethyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

13. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-allylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

14. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N,N-dipropylsulfamoyl-1,3,4-thiadiazol-2-yl)-urea.

15. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-t-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

16. The thiadiazole according to claim 1, which is 1-methyl-3-[5-N-(1,1-dimethoxyethyl-2)-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl]urea.

17. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-chloroethylsulfamoyl-1,3,4-thiadiazol-2-yl)-urea.

18. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-methoxy-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

19. The thiadiazole according to claim 1, which is 1-methyl-3-[5-N-(1-methoxyisopropyl-2)-sulfamoyl-1,3,4-thiadiazol-2-yl]urea.

20. The thiadiazole according to claim 1, which is 1,3-dimethyl-3-(5-N-cyanomethyl-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

21. The thiadiazole according to claim 1, which is 1-methyl-3-(5-N-cyanomethyl-N-butylsulfamoyl-1,3,4-thiadia-zol-2-yl)urea.

22. The thiadiazole according to claim 1, wherein said metal salt is an alkali metal salt.

23. A method of controlling undesirable weeds and plants which comprises applying to said weeds and plants a herbicidally effective amount of a herbicidal composition containing at least one thiadiazole having the formula:

[A]

wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being halo, hydroxy, cyano or lower alkoxy;

R2 is R1 or a lower alkoxy radical, with the proviso that R1 and R2 cannot both be hydrogen;

R3 is hydrogen or a lower acyclic hydrocarbon radical;

R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical; and R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being halo, hydroxy, cyano, or lower alkoxy, with the proviso that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical; or [B] a tautomer of [A], wherein R3 is hydrogen; or [C] a metal or an ammonium salt of [A] wherein R3 is hydrogen;
but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:

when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;

when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;

when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;

when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;

when R1 and R2 are butyl, R3 and R4 are hydrogen and R5 is methyl;

when R1 and R2 are allyl, R3 and R5 are methyl and R4 is hydrogen;

when R1, R3 and R5 are methyl and R2 and R4 are hydro-gen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen;
as the active ingredient, and a carrier or diluent therefor.

24. A method of controlling undesirable weeds and plants which comprises applying to said weeds and plants a herbicidally effective amount of a herbicidal composition containing at least one thiadiazole having the formula:

[A]
wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, and lower alkoxy, R2 is R1 or a lower alkoxy radical, except that R1 and R2 cannot both be hydrogen, R3 is hydrogen or a lower acyclic hydrocarbon radical, R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical, and R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hy-droxy, cyano, or lower alkoxy, except that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical;
or [B] a tautomer of [A] wherein R3 is hydrogen;
but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:

when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;

when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;

when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;

when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;

when R1 and R2 are butyl, R3 and R4 are hydrogen and R5 is methyl;

when R1 and R2 are allyl, R3 and R5 are methyl and R4 is hydrogen;

when R1, R3 and R5 are methyl and R2 and R4 are hydro-gen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen;

as the active ingredient, and a carrier or diluent therefor.

25. A method of controlling undesirable weeds and plants which comprises applying to said weeds and plants a herbicidally effective amount of a herbicidal composition containing at least one thiadiazole having the formula:

wherein R1 is hydrogen or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, and lower alkoxy, R2 is R1 or a lower alkoxy radical, except that R1 and R2 cannot both be hydrogen, R4 is hydrogen, a lower acyclic hydrocarbon radical, or a lower cycloalkyl radical, R5 is hydrogen, a lower cycloalkyl radical, a lower alkoxy radical, or a substituted or unsubstituted lower acyclic hydrocarbon radical, the substituents being selected from the class consisting of halo, hydroxy, cyano, or lower alkoxy, except that R4 and R5 cannot both be hydrogen or a lower cycloalkyl radical, Y is an alkali metal or ammonium radical, and n is the chemical equivalent of Y, but excluding the compounds wherein R1, R2, R4 and R5 have the following definitions:

when R1 is methyl; R2 and R4 are hydrogen and R5 is methyl; and when R1 and R2 are butyl, R4 is hydrogen and R5 is methyl;

as the active ingredient, and a carrier or diluent therefor.

26. The method according to claim 23, wherein the metal salt is an alkali metal salt.

27. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

28. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-butyl-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

29. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-butylsulfamoyl-1,3,4-thia-diazol-2-yl)urea.

30. The method according to claim 23, wherein the thiadiazole is 1-cyclopropyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

31. The method according to claim 23, wherein the thiadiazole is 1-butyl-1-methyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

32. The method according to claim 23, wherein the thiadiazole is 1,3-dimethyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

33. The method according to claim 23, wherein the thiadiazole is 1-methyl-1-methoxy-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

34. The method according to claim 23, wherein the thiadiazole is 1-n-butyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

35. The method according to claim 23, wherein the thiadiazole is 1,1-dimethyl-3-(5-N,N-dimethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

36. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-allylsulfamoyl-1,3,4-thia-diazol-2-yl)urea.

37. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N,N-dipropylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

38. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-t-butylsulfamoyl-1,3,4-thia-diazol-2-yl)urea.

39. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-[5-N-(1,1-dimethoxyethyl-2)-N-methyl-sulfamoyl-1,3,4-thiadiazol-2-yl]urea.

40. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-chloroethylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

41. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-methoxy-N-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

42. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-[5-N-(1-methoxyisopropyl-2)-sulfa-moyl-1,3,4-thiadiazol-2-yl]urea.

43. The method according to claim 23, wherein the thiadiazole is 1,3-dimethyl-3-(5-N-cyanomethyl-N-methylsul-famoyl-1,3,4-thiadiazol-2-yl)urea.

44. The method according to claim 23, wherein the thiadiazole is 1-methyl-3-(5-N-cyanomethyl-N-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

45. A thiadiazole having the formula:
[A] wherein R1 represents hydrogen, lower alkyl radical optionally substituted by cyano or lower alkoxy, lower alkenyl and lower alkynyl, R2 is any of the moieties represented by R1, R3 is hydrogen or lower alkyl of 1 to 2 carbon atoms, R4 is hydrogen or lower alkyl, R5 is hydrogen or lower alkyl with the proviso that radicals R4 and R5 are not both hydrogen, but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:
when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;
when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;
when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;

when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;
when R1 and R2 are butyl; R3 and R4 are hydrogen and R5 is methyl;
when R1 and R2 are allyl; R3 and R5 are methyl and R4 is hydrogen;
when R1, R3 and R5 are methyl and R2 and R4 are hy-drogen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen.

46. A thiadiazole of Formula [A] in claim 45 wherein R1 and R2 together with the nitrogen atom represent a mor-pholine radical.

47. A thiadiazole having the formula:
[A] wherein R1 is hydrogen or alkyl of up to 3 carbon atoms or allyl, R2 is any of the moieties represented by R1 or lower alkoxy of up to 3 carbon atoms, R3 is hydrogen or methyl, R4 is hydrogen or alkyl of up to 3 carbon atoms and R5 is alkyl or alkoxy of up to 3 carbon atoms, but excluding the compounds wherein R1, R2, R3, R4 and R5 have the following definitions:
when R1 is methyl; R2, R3 and R4 are hydrogen and R5 is methyl;
when R1 is methyl; R2 is methoxy; R3 and R5 are methyl and R4 is hydrogen;
when R1, R2 and R3 are ethyl; R4 is hydrogen and R5 is methyl;
when R1 and R2 are ethyl; R3 and R5 are methyl and R4 is hydrogen;
when R1 and R2 are butyl; R3 and R4 are hydrogen and R5 is methyl;
when R1 and R2 are allyl, R3 and R5 are methyl and R4 is hydrogen;
when R1, R3 and R5 are methyl and R2 and R4 are hydro-gen; and when R1 is methoxypropyl, R3 and R5 are methyl and R2 and R4 are hydrogen.

48. The thiadiazole according to claim 46, which is 1-methyl-3-(5-morpholinosulfamoyl-1,3,4-thiadiazol-2-yl)urea .

49. The thiadiazole according to claim 45, which is 1-methyl-3-(5-sulfamoyl-1,3,4-thiadiazol-2-yl)urea.

50. The process of preparing a phytotoxic thiadiazole having the Formula [A] in claim 45, the said process consist-ing of reacting a compound of the formula:
with either a) a carbamoyl chloride or an isocyanate of the for-mula:
R4R5NCOCl or R5NCO

or b) phosgene in an inert solvent, followed by reacting the resulting carbamoyl chloride with an amine of the for-mula:

to yield said phytotoxic thiadiazole wherein R1, R2, R3, R4 and R5 are as defined in claim 45.

51. A process of preparing a phytotoxic thiadiazole having the Formula [A] in claim 45, wherein R4 is hydrogen which comprises reacting a compound of the formula:
with an isocyanate of the formula R5NCO wherein R5 is a lower alkyl radical.

52. A process of preparing a phytotoxic thiadiazole having the Formula [A] in claim 45 wherein R1 and R2 together with the nitrogen atom represent the morpholine radical, the said process consisting of reacting a compound of the formula:
with either a) a carbamoyl chloride or an isocyanate of the for-mula R4R5NCOCl or R5NCO
or b) phosgene in an inert solvent, followed by reacting the resulting carbamoyl chloride with an amine of the for-mula R4R5NH to yield said phytotoxic thiadiazole wherein R3, R4 and R5 are as defined in claim 45.

53. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of a thiadiazole having the Formula [A] as defined in claim 45.

54. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of a thiadiazole having the Formula [A] of claim 45 wherein radicals R1 and R2 together with the nitrogen atom represent a morpholine radical.

55. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of a thiadiazole having the Formula [A] as defined in claim 47.

56. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-N,N-dimethylsulfa-moyl-1,3,4-thiadiazol-2-yl)urea.

57. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1,3-dimethyl-3-(5-N,N-dimethyl-sulfamoyl-1,3,4-thiadiazol-2-yl)urea.

58. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-1-methoxy-3-(5-N,N-di-methylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

59. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-N-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

60. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-morpholinosulfa-moyl-1,3,4-thiadiazol-2-yl)urea.

61. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-n-butyl-3-(5-N,N-dimethylsul-famoyl-1,3,4-thiadiazol-2-yl)urea.

62. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1,1-dimethyl-3-(5-N,N-dimethyl-sulfamoyl-1,3,4-thiadiazol-2-yl)urea.

63. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-N-allylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

64. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-N,N-di-n-propylsul-famoyl-1,3,4-thiadiazol-2-yl)urea.

65. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-N-t-butylsulfamoyl-1,3,4-thiadiazol-2-yl)urea.

66. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of the thiadiazole, 1-methyl-3-(5-sulfamoyl-1,3,4-thiadiazol-2-yl)urea.

67. A thiadiazole of the formula [A] in claim 45 wherein R1 is hydrogen, lower alkyl or lower alkenyl, R2 is any of the moieties represented by R1, R3 is hydrogen or lower alkyl of 1 to 2 carbon atoms, R4 is hydrogen or lower alkyl, and R5 is hydrogen, lower alkyl or lower cycloalkyl wherein R4 and R5 are not both hydrogen.

68. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation an effective amount of a thiadiazole having the Formula [A] of claim 45 as defined in claim 67.

69. A thiadiazole according to claim l wherein R1 and R2 are independently C1-C4 alkyl, optionally substituted with halo, hydroxy, cyano or C1-C2 alkoxy;
R3 and R4 are independently hydrogen or C1-C2 alkyl;
R5 is C1-C2 alkyl;
provided that R1 and R2 are not both ethyl or both butyl.

70. A thiadiazole according to claim 69 wherein R3 is C1-C2 alkyl.

71. A thiadiazole according to claim 70 wherein R1 and R2 are independently C1-C4 alkyl.

72. A method according to claim 23, wherein, in the thiadiazole, R1 and R2 are independent C1-C4 alkyl, option-ally substituted with halo, hydroxy, cyano or C1-C2 alkoxy;
R3 and R4 are independently hydrogen or C1-C2 alkyl;
R5 is C1-C2 alkyl;
provided that R1 and R2 are not both ethyl or both butyl.

73. A method according to claim 72 wherein, in the thiadiazole, R3 is C1-C2 alkyl.

74. A method according to claim 73 wherein, in the thiadiazole, R1 and R2 are independently C1-C4 alkyl.

75. A process of preparing a thiadiazole of claim 69, which comprises reacting a compound of the formula:
with either a) a carbamoyl chloride of an isocyanate having the formula R4R5NCOCl or R5NCO

b) phosgene in an inert solvent, followed by reacting the resulting carbamoyl chloride with an amine of the for-mula R4R5NH to yield said thiadiazole, wherein R1, R2, R3, R4 and R5 are defined as in claim 69.

76. The process according to claim 75, wherein R3 is C1-C2 alkyl.

77. The process according to claim 76, wherein R1 and R2 are independently C1-C4 alkyl.

78. A method of combatting unwanted vegetation by applying to a locus containing unwanted vegetation or sus-ceptible to the growth of unwanted vegetation, an effective amount of a thiadiazole as defined in claim 69.

79. The method according to claim 78 wherein, in the thiadiazole, R3 is C1-C2 alkyl.

80. The method according to claim 79, wherein, in the thiadiazole, R1 and R2 are independently C1-C4 alkyl.