Abstract: 4-Formyltetrahydropyrans of the general formula I ##STR1## where R.sup.1 is hydrogen, C.sub.1 -C.sub.12 -alkyl, C.sub.2 -C.sub.12 -alkenyl, C.sub.1 -C.sub.6 -alkoxy-substituted C.sub.1 -C.sub.12 -alkyl, C.sub.4 -C.sub.12 -cycloalkyl, unsubstituted or substituted aryl, hetaryl or aralkyl, or an unsubstituted or substituted, saturated or unsaturated 5-membered or 6-membered ring which may be interrupted by N, O or S, are prepared by a process in which a pyran derivative of the general formula II ##STR2## where R.sup.1 is as defined above, R.sup.2 and R.sup.3 are each OH or together are an oxygen atom and thus form an oxirane ring, and R.sup.4 is hydrogen where R.sup.2 and R.sup.3 are each OH, and is hydrogen or tert-butoxycarbonyl where R.sup.2 and R.sup.3 together are an oxygen atom, is treated at elevated temperatures with a catalyst selected from the group consisting of zeolites, phosphates, boric acid on a carrier and silica or mixtures of these. Novel 4-formyltetrahydropyrans are also proposed.

Abstract: Cyclohexane-1,3-dione derivatives of the formula ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 have the meanings stated in the description, are used for controlling undesirable plant growth.

Abstract: Cyclohexane-1,3-dione derivatives of the formula ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 have the meanings stated in the description, are used for controlling undesirable plant growth.

Abstract: Cyclohexane-1,3-dione derivatives of the formula ##STR1## where A is tetrahydropyran-4-yl, 3-methyltetrahydropyran-4-yl, 1,4-dioxanyl, 5,5-dimethyl-1,3-dioxan-2-yl, 2,5-dimethyl-1,4-dioxan-3-yl, 2,6-dimethyl-1,4-dioxan-3-yl, 2-methyl-1,3-dithiolan-2-yl, 2,6-dimethyltetrahydrothiopyran-3-yl, 2-methyl-1,3-dithian-2-yl or unsubstituted or substituted 1,3-dioxepan-5-yl, R.sup.1 is hydrogen or methoxycarbonyl, R.sup.2 is alkyl and R.sup.3 is alkyl, alkenyl, haloalkenyl or propargyl, are used for controlling undesirable plant growth of grass species, especially in broadleaved crops and monocotyledon crops which do not belong to the grass family.

Abstract: Cyclohexane-1,3-dione derivatives of the formula ##STR1## where A is an unsubstituted or substituted, saturated or unsaturated 4-membered to 7-membered heterocyclic structure which contains from 1 to 3 nitrogen atoms and may be fused to an aromatic radical, R.sup.1 is hydrogen, methoxycarbonyl, ethoxycarbonyl, methyl or cyano, R.sup.2 is alkyl and R.sup.3 is alkyl, haloalkenyl or propargyl, and salts of these compounds, are useful for controlling undesirable plant growth.

Abstract: Triazolyl ketone-oximes and triazolyl dioximes of the general formula I ##STR1## where Ar is an aryl radical from the group comprising biphenylyl, naphthyl and phenyl, which radical can be substituted by halogen, nitro, cyano or trifluoromethyl, by alkyl, alkoxy or alkenyl, each of not more than 5 carbon atoms or by phenoxy, andn is 1 or 2,X is oxygen or .dbd.N--OR.sup.3, R.sup.3 being hydrogen, unsubstituted, halogen-substituted or alkoxy-substituted alkyl, alkenyl or alkynyl, each of not more than 5 carbon atoms, or benzyl which is unsubstituted or substitutedby halogen, nitro, cyano or trifluoromethyl, or by alkyl or alkoxy, each of not more than 4 carbon atoms, or is --CO--R.sup.4,R.sup.4 being unsubstituted, halogen-substituted or alkoxy-substituted alkyl of not more than 5 carbon atoms, an aromatic radical or --NH--R.sup.5, R.sup.5 being alkyl or not more than 4 carbon atoms or an aromatic radical,R.sup.

Abstract: Urea derivatives of the formula ##STR1## where R, X, Z, Het and n have the meanings given in the description, are used for controlling undesirable plant growth.