Process for the preparation of optically active isoxazoline compounds

1. A process for the preparation of a compound of formula I

wherein

A 1 and A 2 are C—H, or one of A 1 and A 2 is C—H and the other is N;

R 1 is C 1 -C 4 alkyl, C 1 -C 4 haloalkyl or C 3 -C 6 cycloalkyl;

each R 2 is independently bromo, chloro, fluoro or trifluoromethyl;

R 3 is hydrogen;

R 4 is hydrogen, halogen, methyl, halomethyl or cyano;

or R 3 and R 4 together form a bridging 1,3-butadiene group;

R 5 is chlorodifluoromethyl or trifluoromethyl;

n is 2 or 3;

by reacting a compound of formula II

wherein

A 1 , A 2 , R 1 , R 2 , R 3 , R 4 , R 5 and n is as defined under formula I above, with hydroxylamine, a base and a chiral catalyst, characterized in that the chiral catalyst is a dimeric chiral catalyst of formula III

wherein

each R 6 is ethyl or vinyl;

R 7 , R 8 , R 9 and R 10 are halogen, cyano, C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkoxy, C 1 -C 6 alkylthio, C 1 -C 6 haloalkylthio, C 1 -C 6 alkylsulfonyl or C 1 -C 6 haloalkylsulfonyl; and

X is a halogen anion or BF 4 —, PF 6 − , HSO 4 — or an C 1 -C 3 alkylsulfonate, benzenesulfonate or methyl-benzenesulfonate.

2. A process according to claim 1 , wherein in the catalyst of formula III

each R 6 is vinyl;

each of the substituents R 7 , R 8 , R 9 and R 10 has the same meaning and represent halogen and X is chloride or bromide or BF 4 — or PF 6 − .

3. A process according to claim 1 , wherein in the catalyst of formula III

each R 6 is vinyl;

each of the substituents R 7 , R 8 , R 9 and R 10 has the same meaning and represent fluoro or chloro; and

X is chloride or bromide.

4. A process according to claim 1 , wherein the amount of hydroxylamine is from 1 to 10 equivalents.

5. A process according to claim 1 , wherein the amount of base is from 0.05 to 2 equivalents.

6. A process according to claim 1 , wherein the amount of catalyst is from 0.01 to 0.4 equivalents.

7. A compound of formula III

wherein

each R 6 is ethyl or vinyl;

R 7 , R 8 , R 9 and R 10 are halogen, cyano, C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkoxy, C 1 -C 6 alkylthio, C 1 -C 6 haloalkylthio, C 1 -C 6 alkylsulfonyl or C 1 -C 6 haloalkylsulfonyl;

and X is a halogen anion, BF 4 —, PF 6 − or an C 1 -C 3 alkylsulfonate, benzenesulfonate or methyl-benzenesulfonate.

8. A compound of formula III according to claim 7 , wherein

each R 6 is vinyl;

each of the substituents R 7 , R 8 , R 9 and R 10 has the same meaning and represent halogen; and

X is chloride, bromide or BF 4 —.

9. A compound of formula Ill according to claim 7 , wherein

each R 6 is vinyl;

each of the substituents R 7 , R 8 , R 9 and R 10 has the same meaning and represent fluoro or chloro; and

X is chloride or bromide.