Isoxazole derivatives and their use as herbicides

Details Isoxazole derivatives and their use as herbicides Isoxazole derivatives and their use as herbicides

1997-04-29

2001-10-02

McKane, Joseph K. (Department: 1613)

Plant protecting and regulating compositions

Plant growth regulating compositions

Organic active compound containing

C548S243000

Reexamination Certificate

active

06297198

ABSTRACT:

BACKGROUND OF THE INVENTION
Various substituted isoxazoles are known to be useful as herbicides. Typical herbicidal properties of such compounds are described in U.S. Pat. No. 5,489,570 and European Patent Application with Pub. No. 0 418 175 A2.
SUMMARY OF THE INVENTION
This invention relates to a novel class of isoxazole derivatives and their use as herbicides when used in a phytotoxic amount. More specifically, this invention relates to isoxazole derivatives having the formula:
or an agriculturally acceptable salt thereof
In the above formula, the letter R represents a lower alkyl, haloalkyl, alkoxyalkyl, cycloalkyl, or alkenyl, each of which is optionally substituted.
The symbol R
1
represents a lower alkyl, haloalkyl or phenyl group, optionally substituted. X and Y are each independently a hydrogen, hydroxyl, halogen, cyano, alkylsulfenyl, alkylsulfinyl, alkylsulfonyl, acyloxy, carbamoyloxy, alkoxy, alkoxycabonyl, alkylsulfonyloxy, amino, substituted amino, acylmino, sulfamoyloxy, sulfamyl; or X and Y can be combined to be ═O, —S(CH
2
)
m
S— and —O(CH
2
)
m
O—, in which m is 2 or 3.
The symbol Ar represents an aromatic ring moiety optionally substituted with from one to four groups. Additionally, two substituents on adjacent positions of the aromatic ring may be taken together with the two atoms to which they are attached, to form a 5- to 7-membered ring optionally substituted.
The letter Z represents —S—, —SO— or —SO
2
—.
The compounds of the present invention, as will be seen from the data which follows, have utility as both pre-emergence and post-emergence herbicides, against a wide range of plant species.
DETAILED DESCRIPTION OF THE INVENTION
Abbreviations and Definitions
The following abbreviations are used herein: AcOH, acetic acid; Boc, t-butoxycarbonyl; DME, dimethoxyethane; DMF, dimethylformamide; EtOAc, ethyl acetate; NMP, N-methylpyrrolidone; TFA, trifluoroacetic acid.
As used herein, the term “alkyl” refers to a saturated hydrocarbon radical which may be straight-chain or branched-chain (for example, ethyl, isopropyl, t-amyl, or 2,5-dimethylhexyl) or cyclic (for example cyclobutyl, cyclopropyl or cyclopentyl) and contains of from 1 to 24 carbon atoms. This definition applies both when the term is used alone and when it is used as part of a compound term, such as “haloalkyl” and similar terms. Preferred alkyl groups are those containing 1 to 6 carbon atoms, which are also referred to as “lower alkyl.” All numerical ranges in this specification and claims are intended to be inclusive of their upper and lower limits.
The term “alkenyl” as used herein refers to an alkyl group as described above which contains one or more sites of unsaturation.
The term “alkoxy” refers to an alkyl radical as described above which also bears an oxygen substituent which is capable of covalent attachment to another hydrocarbon radical (such as, for example, methoxy, ethoxy and t-butoxy).
The term “aryl” or “aromatic ring moiety” refers to an aromatic substituent which may be a single ring or multiple rings which are fused together, linked covalently or linked to a common group such as an ethylene or methylene moiety. The aromatic rings may each contain heteroatoms, for example, phenyl, naphthyl, biphenyl, diphenylmethyl, 2,2-diphenyl-1-ethyl, thienyl, pyridyl and quinoxalyl. The aryl moieties may also be optionally substituted with halogen atoms, or other groups such as nitro, carboxyl, alkoxy, phenoxy and the like. Additionally, the aryl radicals may be attached to other moieties at any position on the aryl radical which would otherwise be occupied by a hydrogen atom (such as, for example, 2-pyridyl, 3-pyridyl and 4-pyridyl).
By the term “agriculturally acceptable salts” is meant salts the cations of which are known and accepted in the art for the formation of salts for agricultural or horticultural use. Preferably the salts are water-soluble. Suitable acid addition salts formed by compounds of formula I include salts with inorganic acids, for example hydrochlorides, sulphates, phosphates and nitrates and salts with organic acids, for example acetic acid.
The term “herbicide”, as used herein, means a compound which controls or modifies the growth of plants. By the term “herbicidally effective amount” is meant an amount of compound which causes a modifeing effect upon the growth of plants. The term “plants” is meant to include germinant seeds, emerging seedlings and established vegetation, including roots and above ground portions. Such modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, leaf burn, dwarfing and the like.
Isoxazole Derivatives
The compounds of the present invention are represented by the formula:
or an agriculturally acceptable salt thereof.
In the above formula, the letter R represents a lower alkyl, haloalkyl, alkoxyalkyl, cycloalkyl, or alkenyl, each of which is optionally substituted with —SR
2
or —OR
2
, in which R
2
is a lower alkyl group. In preferred embodiments, R is a lower alkyl, haloalkyl or cycloalkyl, more preferably cycloalkyl. In the most preferred embodiments, R is cyclopropyl.
The symbol R
1
represents a lower alkyl, haloalkyl or phenyl group, optionally substituted. Suitable substituents include lower alkyl, lower haoialkyl, halogen and nitro. In preferred embodiments, R
1
is lower alkyl and lower haloalkyl.
The letters X and Y are each independently a hydrogen, hydroxyl, halogen, cyano, alkylsulfenyl, alkylsulllnyl, alkylsulfonyl, acyloxy, carbamoyloxy, alkoxy, alkoxycarbonyl, alkylsulfonyloxy, amino, —NR
3
R
4
, acylamino, sulfamoyloxy, sulfamyl; or X and Y can be combined to be ═O, —S(CH
2
)
m
S— and —(CH
2
)
m
O—, in which m is 2 or 3. Preferably, X and Y are combined to be ═O, —S(CH
2
)
m
S— and —O(CH
2
)
m
O—, in which m is 2 or 3. More preferably, X and Y are combined to be ═O.
The symbol Ar represents an aromatic ring moiety optionally substituted with from one to four groups which are each independently halogen, lower alkyl, haloalkyl, lower alkoxy, lower haloalkoxy, lower alkoxyalkyl, lower alkylthioalkyl, lower alkylsulfonylalkyl, lower alkylsulfinylalkyl, R
3
S—, R
3
SO—, R
3
SO
2
—, R
3
SO
3
—, nitro, cyano, lower alkoxyalkoxy, —COR
4
, —CO
2
R
4
, —CR
5
(═NOR
4
), —NR
5
SO
2
R
4
, —NR
4
R
6
, or —NR
3
R
4
. Preferably, the groups are halogen, lower alkyl, lower haloalkyl, lower alkoxy, lower haloalkoxy, R
3
S—, R
3
SO—, R
3
SO
2
—, nitro, —NR
5
SO
2
R
4
, —NR
4
R
6
, or —NR
3
R
4
. Additionally, two substituents on adjacent positions of the aromatic ring may be taken together with the two atoms to which they are attached, to form a 5- to 7-membered ring optionally substituted. Preferably, two substituents on adjacent positions of the aromatic ring, when attached, will form a 6-member ring.
The symbol R
3
represents a lower alkyl, haloalkyl, or (substituted)phenyl in which the substituents are preferably lower alkyl or halogen; R
4
is hydrogen or lower alkyl: R
5
represents a hydrogen, lower alkyl, alkenyl, alkynyl, cycloalkyl or (substituted)phenyl; and R
6
represents —COR
4
or CO
2
R
4
.
The letter Z represents —S—, —SO— or —SO
2
—.
Compound Preparation
The compounds of the present invention can be prepared by a synthetic scheme as outlined in FIG. 1. &bgr;-diketones (I in FIG. 1) can be prepared according to known literature methods (see, for example, Trebs, et al.,
Chef Ber
. 87:1163 (1954); Hauser et al. ORGANC REACTIONS 8:59 (1954); and Rathke, etal.,
J. Org. Chem
. 50:2622 (1985)). Conversion of the &bgr;-diketones to ketene dithioacetals II (R=lower alkyl) can be carried out based on known procedures described in Villemin, et al.,
Synthesis
301 (1991), Pak, et al.,
Synthesis
793 (1988) and Augustin, et al.,
Tetrahedron
32:3055 (1976). For those embodiments in which R=(substituted)phenyl in III, transketalization of II is carried out using (substituted)thiophenol at room temperature or at elevated temperature in organic solvents such as ethanol, tetrahy

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