Process for preparing 3-arylmethylthio- and 3-heteroarylmethylthio-4,5-dihydroisoxazoline derivatives

1 . A process for preparing a 3-arylmethylthio- or a 3-heteroarylmethylthio-4,5-dihydroisoxazoline derivative of the formula (I)

where

R 1 , R 2 are each independently hydrogen, (C 1 -C 6 )-alkyl, (C 2 -C 6 )-alkenyl, (C 2 -C 6 )-alkynyl or (C 3 -C 8 )-cycloalkyl, where each of the (C 1 -C 6 )-alkyl, (C 2 -C 6 )-alkenyl, (C 2 -C 6 )-alkynyl or (C 3 -C 8 )-cycloalkyl radical is unsubstituted or substituted by one or more identical or different radicals selected from the group consisting of halogen, cyano, (C 3 -C 8 )-cycloalkyl, —OR 7 and —S(O) m R 7 where m=0, 1 or 2, and R 7 is (C 1 -C 6 )-alkyl, (C 3 -C 6 )-alkenyl, (C 3 -C 6 )-alkynyl, or (C 3 -C 8 )-cycloalkyl, each of which is unsubstituted or substituted by one or more identical or different radicals selected from the group consisting of halogen and cyano,

or R 1 and R 2 together with the carbon atom to which they are both attached form a spiro linkage composed of from 3 to 8 carbon atoms,

R 3 , R 4 are each independently hydrogen, (C 1 -C 6 )-alkyl, (C 2 -C 6 )-alkenyl, (C 2 -C 6 )-alkynyl or (C 3 -C 8 )-cycloalkyl, where the (C 1 -C 6 )-alkyl, (C 2 -C 6 )-alkenyl, (C 2 -C 6 )-alkynyl or (C 3 -C 8 )-cycloalkyl group is optionally substituted by one or more identical or different radicals selected from the group consisting of halogen, cyano, (C 3 -C 8 )-cycloalkyl, (C 1 -C 6 )-alkoxy, (C 1 -C 6 )-haloalkoxy and (C 1 -C 6 )-alkylthio,

or R 3 and R 4 together with the carbon atom to which they are attached form a spiro linkage composed of from 3 to 8 carbon atoms,

or R 1 and R 3 together with the carbon atoms to which they are attached form a ring structure consisting of 5-8 carbon atoms,

R 5 is unsubstituted or substituted aryl, or unsubstituted or substituted heteroaryl, where the aryl or heteroaryl group is optionally substituted by OH, halogen, cyano, (C 1 -C 6 )-alkyl, (C 1 -C 6 )-haloalkyl, (C 2 -C 6 )-alkenyl, (C 2 -C 6 )-alkynyl, (C 3 -C 8 )-cycloalkyl, (C 3 -C 6 )-cycloalkenyl, mono-(C 1 -C 6 )-alkylamino, di-((C 1 -C 6 )-alkyl)amino, N-((C 1 -C 6 )-alkanoyl)-amino, (C 1 -C 6 )-alkoxy, (C 1 -C 6 )-haloalkoxy, (C 3 -C 6 )-alkenyloxy, (C 3 -C 6 )-alkynyloxy, (C 3 -C 6 )-cycloalkoxy, (C 4 -C 6 )-cycloalkenyloxy, (C 1 -C 6 )-alkylthio, (C 1 -C 6 )-haloalkylthio, (C 3 -C 6 )-cycloalkylthio, (C 3 -C 6 )-alkenylthio, (C 4 -C 6 )-cycloalkenylthio, (C 3 -C 6 )-alkynylthio, (C 1 -C 6 )-alkanoyl, (C 2 -C 6 )-alkenylcarbonyl, (C 2 -C 6 )-alkynylcarbonyl, arylcarbonyl, (C 1 -C 6 )-alkylsulfinyl, (C 1 -C 6 )-alkylsulfonyl, (C 1 -C 6 )-haloalkylsulfinyl or (C 1 -C 6 )-haloalkylsulfonyl, and

R 6 is hydrogen or (C 1 -C 6 )-alkyl, comprising

allowing an arylmethyl- or a heteroarylmethylisothiuronium salt of the formula (II)

in which R 5 and R 6 are each as defined above for the formula (I) and Lg is a leaving group,

to react in a one-pot process in the presence of an aqueous alkali metal or alkaline earth metal base with an isoxazoline derivative of the formula (IV)

in which R 1 , R 2 , R 3 and R 4 are each as defined above for the formula (I) and Lg′ is a leaving group

to give the corresponding 3-arylmethylthio- or 3-heteroarylmethylthio-4,5-dihydroisoxazoline derivative of the formula (I).

2 . The process as claimed in claim 1 , wherein R 1 and R 2 are each independently (C 1 -C 4 )-alkyl, (C 2 -C 3 )-alkenyl, (C 2 -C 3 )-alkynyl, or (C 3 -C 6 )-cycloalkyl, and where each of the (C 1 -C 4 )-alkyl, (C 2 -C 3 )-alkenyl, (C 2 -C 3 )-alkynyl, or (C 3 -C 6 )-cycloalkyl radicals is optionally substituted by one or more radicals selected from the group consisting of halogen, cyano and (C 3 -C 6 )-cycloalkyl.

3 . The process as claimed in claim 2 , where R 1 and R 2 are each independently (C 1 -C 4 )-alkyl or (C 1 -C 4 )-haloalkyl.

4 . The process as claimed in claim 2 , wherein R 1 and R 2 are each independently methyl or ethyl each of which is optionally independently mono- or polyhalogenated.

5 . The process as claimed in claim 4 , wherein R 1 and R 2 are each independently methyl, ethyl or chloromethyl.

6 . The process as claimed in claim 5 , wherein R 1 and R 2 are each independently methyl or ethyl.

7 . The process as claimed in claim 1 , wherein R 3 and R 4 are each independently hydrogen or (C 1 -C 4 )-alkyl.

8 . The process as claimed in claim 7 , wherein R 3 and R 4 are both hydrogen.

9 . The process as claimed in claim 1 , wherein R 5 is an unsubstituted or substituted aryl having from 6 to 10 carbon atoms or unsubstituted or substituted heteroaryl having from 3 to 5 carbon atoms and from 1 to 3 heteroatoms selected from the group consisting of N, O and S, where each of the aryl or heteroaryl radicals is optionally substituted by one or more identical or different radicals selected from the group consisting of halogen, cyano, ethyl, methyl, haloethyl, halomethyl, halomethoxy and haloethoxy.

10 . The process as claimed in claim 9 , wherein R 5 is a substituted or unsubstituted phenyl, naphthyl, thienyl, furyl, pyrazolyl, pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, imidazolyl, isothiazolyl, thiazolyl or oxazolyl optionally substituted by one or more identical or different radicals selected from the group consisting of halogen, cyano, ethyl, methyl, halomethoxy and halomethyl.

11 . The process as claimed in claim 1 , wherein the leaving group Lg is chlorine, bromine, iodine or a sulfonate group.

12 . The process as claimed in claim 1 , wherein the leaving group Lg′ is chlorine, bromine, or a sulfonate group, or a methylsulfonyl group.

13 . The process as claimed in claim 1 , wherein the leaving group Lg′ is chlorine.

14 . The process as claimed in claim 1 , wherein the compound of the formula (II) is reacted with an equimolar amount of the compound of the formula (IV) under phase transfer conditions with vigorous stirring.

15 . The process as claimed in claim 14 , wherein a biphasic system is used, comprising an aqueous, strongly basic alkali metal or alkaline earth metal hydroxide solution, and an organic phase which is an inert solvent or a mixture of inert solvents.

16 . The process as claimed in claim 15 , further comprising a phase transfer catalyst selected from the group consisting of a quaternary ammonium salt, a quaternary phosphonium salt, a crown ether, a cryptand and a polyethylene glycol.

17 . The process as claimed in claim 14 , wherein the reaction temperature is from −10° C. to 150° C.

18 . The process as claimed in claim 17 , wherein the compounds of formula (II) and formula (IV) are stirred vigorously under a protective gas atmosphere at a temperature of from 20° C. to 100° C.

19 . The process as claimed in claim 11 , wherein the sulfonate group is selected from the group consisting of methane-, trifluoromethane-, ethane-, benzene- and toluenesulfonate.

20 . The process as claimed in claim 12 , wherein the sulfonate group is selected from the group consisting of methane-, trifluoromethane-, ethane-, benzene- and toluenesulfonate.

21 . The process as claimed in claim 14 , wherein the compound of the formula (II) is obtained by crystallization and is used without further purification steps.

22 . The process as claimed in claim 15 , wherein the organic phase is an inert solvent selected from the group consisting of tetrahydrofuran, diethyl ether, acetonitrile, pentane, hexane, benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, nitrobenzene and mixtures thereof.