Preparation of isoxazolin-3-ylacylbenzenes
A process is described for preparing isoxazoles of the formula I where the substituents are as defined below: R 1 is hydrogen, C 1 -C 6 -alkyl, R 2 is C 1 -C 6 -alkyl, R 3 , R 4 , R 5 are hydrogen, C 1 -C 6 -alkyl, or R 4 and R 5 together form a bond, R 6 is a heterocyclic ring, n is 0, 1 or 2; which comprises preparing an intermediate of the formula VI where R1, R3, R4 and R5 are as defined above, followed by halogenation, thiomethylation, oxidation and acylation to give compounds of the formula I. Also novel intermediates for preparing the compounds of the formula I and novel processes for preparing the intermediates are described.
1. A process for preparing a thioether of formula XIX
wherein
R x is hydrogen, alkyl, haloalkyl, halogen, cyano, nitro, alkoxy, haloalkoxy, alkylthio, or a saturated, unsaturated or partially unsaturated heterocycle having one, two or three oxygen, sulfur or nitrogen atoms,
m is a number from 0 to 5, and
R 2 is C 1 -C 6 -alkyl,
which comprises reacting an aniline of formula XX
with a dialkyl disulfide of formula VII
R 2 —S—S—R 2 VII
in the presence of a catalyst and an organic nitrite.
2. A process as claimed in claim 1 , wherein the catalyst is copper powder or elemental copper.
3. A process as claimed in claim 1 , wherein the nitrite is a C 1 -C 6 -alkylnitrite.
4. A process as claimed in claim 1 , wherein R x represents hydrogen, alkyl, haloalkyl, halogen, cyano, nitro, alkoxy, haloalkoxy, alkylthio, or represents an unsubstituted or alkyl-substituted 5-membered heterocyclic saturated, partially saturated or aromatic ring selected from the group consisting of isoxazolines, isoxazoles, thiazolines, thiazoles, oxazoles and pyrazoles.
5. A process as claimed in claim 1 , wherein m is 1, 2 or 3.
6. A process as claimed in claim 1 , wherein m is at least 1 and one group R x is in the ortho or the meta position relative to the group —S—R 2 in formula XIX and in the ortho or the meta position relative to the group —NH 2 in formula XX, respectively.