Substituted piperidines

1. A compound of the formula

in which

R 1 is trifluoromethyl, 1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, difluoromethoxy, trifluoromethoxy or ethyl,

R 2 is 2-hydroxyeth-1-yl, 2-methoxyeth-1-yl, 2-ethoxyeth-1-yl, cyclopropyl or 1-methoxycycloprop-1-yl,

R 3 is a group of the formula

where

* is the point of attachment to the carbonyl group,

or a salt thereof.

2. A compound according to claim 1 , characterized in that

R 1 is trifluoromethyl, 2,2,2-trifluoroethyl, trifluoromethoxy or ethyl,

R 2 is 2-methoxyeth-1-yl, cyclopropyl or 1-methoxycycloprop-1-yl,

R 3 is a group of the formula

where

* is the point of attachment to the carbonyl group.

3. A compound according to claim 1 , characterized in that

R 1 is trifluoromethoxy.

R 2 is 2-methoxyeth-1-yl or cyclopropyl, and

R 3 is a group of the formula

where

* is the point of attachment to the carbonyl group.

4. A compound according to claim 1 , characterized in that the phenyl substituent and the 1,2,4-oxadiazol-5-yl substituent which are bonded to the piperidine ring are in cis positions to one another.

5. A process for preparing a compound of the formula (I) according to claim 1 or a salt thereof, characterized in that

[A] a compound of the formula

in which

R 1 and R 2 are each as defined in claim 1

is reacted with a compound of the formula

in which

R 3 is as defined in claim 1 , and

X 1 is halogen, preferably bromine or chlorine, or hydroxyl or 4-nitrophenoxy,

or

[B] a compound of the formula (II) is reacted in the first stage with 4-nitrophenyl chloroformate and in the second stage with a compound of the formula

R 3 —H  (IV)

in which

R 3 is as defined in claim 1

or

[C] a compound of the formula

in which

R 1 and R 3 are each as defined in claim 1 ,

is reacted with a compound of the formula

in which

R 2 is as defined in claim 1 ,

or

[D] a compound of the formula

in which

R 1 and R 2 are each as defined in claim 1 ,

is reacted with 0.8 to 1.1 equivalents of meta-chloroperbenzoic acid to give a compound of the formula

in which

R 1 and R 2 are each as defined in claim 1 ,

or

[E] a compound of the formula (Ia) is reacted with 2.0 to 3.0 equivalents of meta-chloroperbenzoic acid to give a compound of the formula

in which

R 1 and R 2 are each as defined in claim 1 .

6. A pharmaceutical composition comprising a compound according to claim 1 and an inert nontoxic pharmaceutically acceptable excipient.

7. A compound according to claim 1 , characterized in that:

R 1 is trifluoromethoxy

R 2 is cyclopropyl, and

R 3 is a group of the formula

where

* is the point of attachment to the carbonyl group or a salt thereof.

8. A compound according to claim 1 , wherein the carbon atom to which the phenyl substituent is bonded is in an S configuration and the carbon atom to which the 1,2,4-oxadiazol-5-yl substituent is bonded is also in an S configuration.

9. A compound of formula (a):

10. A compound according to claim 9 , wherein the compound is a cis stereoisomer.

11. A compound according to claim 9 , wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration.

12. A cis stereoisomer of a compound of formula (a):

which is substantially free of the other cis stereoisomer.

13. A stereoisomer of a compound of formula (a):

wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration, which is substantially free of other stereoisomers.

14. A cis stereoisomer of a compound of formula (a):

which is enantiomerically pure.

15. An enantiomerically pure compound of formula (a):

wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration.

16. A compound of claim 14 , wherein the enantiomeric excess is at least 99.0%.

17. A compound of claim 15 , wherein the enantiomeric excess is at least 99.0%.

18. A compound of the formula (a):

or a salt thereof.

19. A compound according to claim 18 , wherein the compound is a cis stereoisomer, or a salt thereof.

20. A compound according to claim 18 , wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration, or a salt thereof.

21. A cis stereoisomer of a compound of formula (a):

or a salt thereof, which is substantially free of the other cis stereoisomer, and is substantially free of any salts of the other cis stereoisomer.

22. A stereoisomer of a compound of formula (a):

or a salt thereof, wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration, which is substantially free of other stereoisomers, and is substantially free of any salts of other stereoisomers.

23. A cis stereoisomer of a compound of formula (a):

or a salt thereof, which is enantiomerically pure.

24. An enantiomerically pure compound of formula (a):

or a salt thereof, wherein the carbon atom to which the trifluoromethoxy-phenyl substituent is bonded is in an S configuration, and wherein the carbon atom to which the 3-cyclopropyl-1,2,4-oxadizol-5-yl substituent is bonded is also in an S configuration.

25. A compound of claim 23 , wherein the enantiomeric excess is at least 99.0%.

26. A compound of claim 24 , wherein the enantiomeric excess is at least 99.0%.

27. A pharmaceutical composition comprising a compound according to any of claims 9 - 26 , and an inert nontoxic pharmaceutically acceptable excipient.