Abstract: The present invention relates to a process for preparing 1-substituted 5-chloro-4-methylpyrazoles of the general formula I with the meaning for R stated in claim 1, in which a 4-methylpyrazole of the formula II is reacted with chlorine, the resulting mixture of monochlorinated and dichlorinated product is fractionated by distillation, and subsequently the dichlorinated compound is dehalogenated to compound II and returned to the reaction with chlorine.

Abstract: The present invention relates to a process for preparing 1-substituted 5-chloro-4-methylpyrazoles of the general formula I 1

Abstract: In a process for preparing 4-amino-5-chloro-1-phenylpyridazin-6-one by reacting 4,5-dichloro-1-phenylpyridazin-6-one with aqueous ammonia in the presence of a catalyst, the catalyst used is soluble in the aqueous alkaline reaction medium but is essentially insoluble in the reaction medium which has been acidified after removal of the 4-amino-5-chloro-1-phenylpyridazin-6-one. The process of the present invention makes it possible for the catalyst to be recovered and reused in a simple manner.

Abstract: The present invention relates to a process for preparing N-substituted 2-pyrazolin-5-ones of the formula I where R has the meaning given in claim 1, which comprises reacting a compound of the formula II where R, X and Y have the meanings given in claim 1, at elevated temperature with a molar excess of alkali metal hydroxide in an aqueous reaction medium and then adjusting the pH to pH≦6 by adding an acid.

Abstract: A process for preparing 3-isopropyl-1H-2,1,3-benzothiadiazin-4 (3H)-one 2,2-dioxide (I) or a salt of I which comprises reacting anthranilic isopropylamide II simultaneously with sulfur trioxide or chlorosulfonic acid in the presence of an organic base or with adducts of sulfur trioxide and organic bases and phosphorus oxychloride at from 50° C. to the reflux temperature, followed, if appropriate, by conversion into its salts, is described.

Abstract: Pyrazole derivatives are prepared by reacting carbonyl compounds R1—C(O)—CH(R2)—CH2R3 with hydrazine, its hydrate or its salts in 30 to 100% by weight sulfuric acid in the presence of catalytic amounts of iodine or of an iodine compound.

Abstract: Process for preparing solid, free-flowing water-soluble salts of aryloxy-C.sub.1 -C.sub.4 -alkanecarboxylic acids by reacting the aryloxy-C.sub.1 -C.sub.4 -alkanecarboxylic acids with a salt-forming base, the salt formation taking place in the melt in the presence or absence of an entraining agent suitable for the azeotropic removal of water or in solution in the presence of an entraining agent suitable for the azeotropic removal of water and, if appropriate, removing the entraining agent from the reaction mixture during the reaction or subsequently and then isolating the solid salts in a customary manner.

Abstract: A process for the preparation of 1,2-dimethyl-3,5-diaryl-pyrazolium methylsulfates of the formula I ##STR1## where R.sup.1 and R.sup.2 independently of one another are hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.3 -C.sub.8 -cycloalkyl, C.sub.1 -C.sub.4 -alkoxy, halogen, nitro, C.sub.1 -C.sub.4 -haloalkyl or aryl all of which are inert under the reaction conditions, in which 1-methyl-3,5-diarylpyrazoles of the formula II ##STR2## where R.sup.1 and R.sup.2 have the abovementioned meanings are reacted witha) methanol and SO.sub.3,b) methanol and sulfuric acid or optionally,c) methanol and methylsulfuric acidelevated temperatures.

Abstract: A process for the preparation of an N-alkyl- or N-phenylalkyl-substituted pyrazole I by reacting the corresponding N-unsubstituted pyrazole II with an alcohol III of the formula R.sup.1 --OH where R.sup.1 is the same alkyl or phenylalkyl group to be added to the unsubstituted nitrogen group --NH-- of the pyrazole reactant. Both of the reactants, i.e. the pyrazole II and alcohol III compounds, are catalytically reacted in the liquid phase in a molar ratio of from 0.001:1 to 1:1, at temperatures of 50.degree.-400.degree. C. and under a subatmosheric pressure of from 0.8 bar up to a superatmospheric pressure of 250 bar. The catalyst required for this liquid phase reaction is selected as being at least one or more non-heterogeneous acid catalysts, their alkyl esters or their acid anhydrides.

Abstract: The present invention relates to a process for the preparation of optically active 2--halopropionic acids, in which the corresponding optically active alkyl 2--halopropionates are caused to react with a carboxylic acid at elevated temperature in a transacylation reaction with the formation of the optically active 2--halopropionic acid and the alkyl carboxylate, and the optically active 2--halopropionic acid obtained is separated from the reaction mixture. The optically active products produced are important intermediates for the preparation of plant protectants and pharmaceuticals.

Abstract: A process for preparing 3,5-diarylpyrazoles of the general formula I ##STR1## where the substituents have the following meanings: R.sup.1 and R.sup.3 are unsubstituted or substituted aryl radicals, R.sup.2 is hydrogen, C.sub.1 -C.sub.8 -alkyl or unsubstituted or substituted aryl,in which hydrazine hydrate is reacted with a 1,3-diarylpropenone of the general formula II ##STR2## where the substituents R.sup.1, R.sup.2 and R.sup.3 have the abovementioned meanings, in sulfuric acid in the presence of iodine or an iodine compound, is described.

Abstract: A process for preparing pyrazole and its derivatives of the formula I ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen, halogen, nitro, carboxyl, sulfonyl or C-organic radicals, from alpha,beta-unsaturated carbonyl compounds of the formula II ##STR2## and hydrazine or hydrazine derivatives of the formula IIIH.sub.2 N--NHR.sup.4 IIIwherein, initially without additional diluent, an alpha,beta-unsaturated carbonyl compound of the formula II is reacted with hydrazine or a hydrazine derivative of the formula III, and the resulting reaction mixture is reacted in another step with a mixture of sulfuric acid and iodine or a compound which liberates iodine or hydrogen iodide.

Abstract: 3-Methylpyrazole and its derivatives are prepared by reacting butenediols or ethynylalkylcarbinols or their acylates in 30-100% by weight sulfuric acid with unsubstituted or substituted hydrazine or its salts in the presence of catalytic amounts of iodine or an iodine compound.

Abstract: Pyrazole and its derivatives are prepared by dehydrogenating 2-pyrazoline or its derivatives by a process in which the reaction is carried out using sulfuric acid in the presence of iodine or of an iodine compound at from 50.degree. to 250.degree. C.