Isoxazole- and isothiazole-5-carboxamides of the formula ##STR1## where X is oxygen or sulfur, R.sup.1 is hydrogen, substituted or unsubstituted alkyl, cycloalkyl, cycloalkenyl, alkenyl (may be epoxidized at the double bond), alkynyl, alkoxy, a heterocyclic radical or phenyl, R.sup.2 is a derivative carboxylic acid function and R.sup.3 and R.sup.4 have the meanings given in the disclosure, and herbicidal agents containing compounds I.

The present invention relates to carboxamides of the formula I 
##STR2## 
where X is oxygen or sulfur; 
R.sup.1 is hydrogen, C.sub.1 -C.sub.6 -alkyl which can carry from one to 
five halogen atoms and/or one or two of the following: 
C.sub.1 -C.sub.3 -alkoxy, C.sub.1 -C.sub.3 -haloalkoxy, cyano or phenyl 
which can be up to trisubstitued by halogen, C.sub.1 -C.sub.3 -alkyl, 
C.sub.1 -C.sub.3 -haloalkyl, C.sub.1 -C.sub.3 -alkoxy, C.sub.1 -C.sub.3 
-haloalkoxy, cyano or nitro; 
C.sub.3 -C.sub.8 -cycloalkyl-substituted C.sub.1 -C.sub.6 -alkyl; 
C.sub.3 -C.sub.6 -cycloalkyl or C.sub.3 -C.sub.6 -cycloalkenyl, each of 
which can be mono- to trisubstituted by C.sub.1 -C.sub.4 -alkyl or 
halogen; 
C.sub.2 -C.sub.6 -alkenyl whose double bond can be epoxidized, or C.sub.2 
-C.sub.6 -alkynyl, where both groups can be mono- to trisubstitute by 
halogen, C.sub.1 -C.sub.3 -alkoxy and/or monosubstituted by cyclopropyl or 
phenyl, where the phenyl can additionally carry up to three of the 
following substituents: 
C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 
-alkoxy, C.sub.1 -C.sub.4 -haloalkoxy, halogen, cyano or nitro; 
C.sub.1 -C.sub.4 -alkoxy; 
a 5- or 6-membered heterocyclic radical with one or two hereto atoms 
selected from oxygen, sulfur and nitrogen, which can carry one or two of 
the following substituents: 
C.sub.1 -C.sub.3 -alkyl, halogen, C.sub.1 -C.sub.3 -alkoxy, carboxyl or 
C.sub.1 -C.sub.3 -alkoxycarbonyl; 
phenyl which can carry from one to three of the following: 
C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.3 -haloalkyl, C.sub.1 -C.sub.3 
-alkoxy, C.sub.1 -C.sub.3 -haloalkoxy, C.sub.1 -C.sub.3 -alkylthio, 
C.sub.1 -C.sub.3 -haloalkylthio, halogen, nitro and cyano, 
R.sup.2 is haloformyl, COYR.sup.5 or CONR.sup.6 R.sup.7, where 
Y is oxygen or sulfur 
R.sup.5 is C.sub.1 -C.sub.6 -alkyl which carries one of the following: 
C.sub.5 -C.sub.6 -cycloalkaniminoxy, a 5- or 6-membered saturated or 
aromatic heterocyclic radical with from one to three hetero atoms selected 
from oxygen, sulfur and nitrogen, except unsubstituted thienyl, furyl, 
tetrahydrofuryl and pyridyl, it not being possible for two oxygen and/or 
sulfur atoms to be directly adjacent, and where the heterocycles can also 
carry one or two of the following substituents: 
halogen, C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.3 -alkoxy or C.sub.1 
-C.sub.3 -alkoxycarbonyl, 
--CR.sup.10 .dbd.N--R.sup.11 where 
R.sup.10 is hydrogen or C.sub.1 -C.sub.6 -alkyl and R.sup.11 is C.sub.1 
-C.sub.6 -alkoxy, C.sub.3 -C.sub.6 -alkenyloxy or C.sub.3 -C.sub.6 
-alkynyloxy, each of which can carry up to three halogen atoms and/or one 
phenyl with, if desired, up to three of the following: halogen, nitro, 
cyano, C.sub.1 -C.sub.3 -alkyl or C.sub.1 -C.sub.3 -alkoxy; phenoxy which 
can carry up to three of the following substituents: 
halogen, nitro, cyano, C.sub.1 -C.sub.3 -alkyl or C.sub.1 -C.sub.3 -alkoxy; 
C.sub.1 -C.sub.6 -alkylamino, di(C.sub.1 -C.sub.6 -alkyl)amino or 
phenylamino, where the aromatic ring can carry up to three of the 
following halogen, nitro, cyano, C.sub.1 -C.sub.3 -alkyl or C.sub.1 
-C.sub.3 -alkoxy; 
R.sup.5 is also a 5- or 6-membered saturated or aromatic heterocyclic 
radical with one or two hereto atoms selected from oxygen, sulfur or 
nitrogen, it not being possible for two oxygen and/or sulfur atoms to be 
directly adjacent, and where the heterocycles can carry one or two of the 
following substituents: halogen, C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.3 
-alkoxy or C.sub.1 -C.sub.3 -alkoxycarbonyl; 
a 5- or 6-membered saturated-or aromatic heterocyclic radical with three 
hereto atoms selected from oxygen, sulfur or nitrogen, it not being 
possible for two oxygen and/or sulfur atoms to be directly adjacent, and 
where the heterocycles can carry one-or two of the following substituents: 
halogen, C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.3 -alkoxy or C.sub.1 
-C.sub.3 -alkoxycarbonyl; 
C.sub.3 -C.sub.8 haloalkynyl; 
--N.dbd.CR.sup.8 R.sup.9 where R.sup.8 is C.sub.1 -C.sub.3 -alkoxy, C.sub.1 
-C.sub.4 -haloalkyl, C.sub.1 -C.sub.3 -alkoxy-C.sub.1 -C.sub.5 -alkyl or 
phenyl-C.sub.1 -C.sub.5 -alkyl, it being possible for the phenyl in turn 
to be mono- to trisubstituted by halogen, nitro, cyano, C.sub.1 -C.sub.3 
-alkyl, C.sub.1 -C.sub.3 -haloalkyl, C.sub.1 -C.sub.3 -alkoxy or C.sub.1 
-C.sub.3 -haloalkoxy and R.sup.9 is C.sub.1 -C.sub.4 -alkyl; 
##STR3## 
where R.sup.3 is hydrogen or C.sub.1 -C.sub.5 -alkyl and 
R.sup.14 is C.sub.1 -C.sub.5 -alkyl which can be substituted by C.sub.1 
-C.sub.4 -alkanoyl or benzoyl which can be substituted by halogen or 
C.sub.1 -C.sub.3 -alkyl; 
--W--Z where W is a C.sub.2 -C.sub.4 -alkylene chain, ethoxyethylene, 
2-butenylene or 2-butynylene, and Z is a part of the molecule which is 
bonded in the .omega. position to W and which represents the same part of 
the molecule which is linked to W in the .alpha. position of W; 
R.sup.6 is hydrogen, C.sub.1 -C.sub.5 -alkyl or C.sub.3 -C.sub.8 
-cycloalkyl and 
R.sup.7 is --C(OR.sup.12).dbd.NH or --C(OR.sup.12).dbd.N--(C.sub.1 
-C.sub.4)-alkyl, where R.sup.12 is C.sub.1 -C.sub.4 -alkyl, 
R.sup.3 is hydrogen; 
C.sub.1 -C.sub.6 -alkyl which can carry from one to three of the following 
substituents: hydroxyl, halogen, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 
-C.sub.4 -alkylthio or di-(C.sub.1 -C.sub.4)-alkylamino; 
C.sub.3 C.sub.8 -cycloalkyl which can be mono- to trisubstituted by 
halogen, C.sub.1 -C.sub.4 -alkyl and partially or completely halogenated 
C.sub.1 -C.sub.4 -alkyl; 
R.sup.4 is hydrogen, hydroxyl, C.sub.1 -C.sub.4 -alkoxy; 
C.sub.1 -C.sub.6 -alkyl which can carry from one to three of the following 
halogen, cyano, C.sub.1 -C.sub.4 -alkoxy, partially or completely 
halogenated C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkylthio, 
partially or completely halogenated C.sub.1 -C.sub.4 -alkylthio, 
di-C.sub.1 -C.sub.4 -alkylamino, C.sub.3 -C.sub.8 -cycloalkyl or phenyl, 
where the phenyl ring in turn can carry one to three of the following 
halogen, cyano, nitro, C.sub.1 -C.sub.4 -alkyl, partially or completely 
halogenated C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 
-C.sub.4 -alkylthio or partially or completely halogenated C.sub.1 
-C.sub.4 -alkoxy or C.sub.1 -C.sub.4 -alkylthio; C.sub.3 -C.sub.8 
-cycloalkyl which can carry from one to three of the following: halogen, 
nitro, cyano, C.sub.1 -C.sub.6 -alkyl, partially or completely halogenated 
C.sub.1 -C.sub.6 -alkyl, C.sub.1 -C.sub.4 -alkoxy or partially or 
completely halogenated C.sub.1 -C.sub.4 -alkoxy; 
C.sub.3 -C.sub.6 -alkenyl whose double bond can be epoxidized, or C.sub.3 
-C.sub.6 -alkynyl, each of which can be mono- to trisubstituted by halogen 
and/or monosubstituted by phenyl, where the phenyl in turn can carry from 
one to three of the following: C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 
-haloalkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -haloalkoxy, 
C.sub.1 -C.sub.4 -alkylthio, C.sub.1 -C.sub.4 -haloalkylthio, halogen, 
cyano or nitro; 
di-(C.sub.1 -C.sub.4)-alkylamino; 
a 5- or 6-membered heterocyclic, saturated or aromatic radical with one or 
two hereto atoms selected from oxygen, sulfur and nitrogen, which can be 
mono- to trisubstituted by C.sub.1 -C.sub.4 -alkyl or halogen; 
phenyl which can carry from one to four of the followings C.sub.1 -C.sub.4 
-alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 
-C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -alkylthio, C.sub.1 -C.sub.4 
-haloalkylthio, halogen, nitro, cyano, formyl, C.sub.2 -C.sub.4 -alkanoyl, 
C.sub.2 -C.sub.4 -haloalkanoyl or C.sub.1 -C.sub.4 -alkoxycarbonyl; 
naphthyl which can be mono- to trisubstituted by C.sub.1 -C.sub.4 alkyl or 
halogen; 
or 
R.sup.3 and R.sup.4 together form a tetra- to heptamethylene chain which 
can be interrupted by oxygen, sul fur or N-methyl, or --(CH.sub.2).sub.3 
--CO--, 
with the proviso that R.sup.5 is not C.sub.3 -C.sub.6 -haloalkynyl when 
R.sup.1 is unsubstituted or substituted C.sub.2 -C.sub.6 -alkenyl, whose 
double bond can be epoxidized, unsubstituted or substituted C.sub.3 
-C.sub.6 -cycloalkenyl, unsubstituted or substituted C.sub.2 -C.sub.6 
-alkynyl or C.sub.3 -C.sub.8 -cycloalkyl-substituted C.sub.1 -C.sub.5 
-alkyl; 
and the environmentally acceptable salts of the compound I. 
The present invention also relates to herbicidal agents which contain the 
compounds I as active ingredients and to the processes for preparing the 
compounds I. 
Herbicidal isoxazole- and isothiazole-5-carboxamides and their derivatives 
are disclosed in DE-A-3,812,225. Despite the intrinsically good herbicidal 
activity of the known products, it is an object of the present invention 
to provide compounds with-improved properties, especially with regard to 
crop selectivity or environmental behavior. 
We have found that this object is achieved by the isoxazole- and 
isothiazole-5-carboxamide defined in the introduction.