Substituted imidazol-pyridazine derivatives

1. A compound of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable acid addition salt thereof.

2. The compound of claim 1 , wherein A is the group

wherein

R 1 -R 4 are each independently selected from hydrogen, halogen, CF 3 , CHF 2 ,C(CH 3 )F 2, C 3 -C 6 -cycloalkyl, lower alkoxy, lower alkyl, OCF 3 and phenyl.

3. The compound of claim 1 , wherein A is the group

wherein

R 5 -R 10 are each independently selected from hydrogen, halogen, lower alkyl, lower alkoxy and CHF 2 .

4. The compound of claim 1 , wherein A is the group

wherein

R 11 -R 16 are each independently selected from hydrogen, halogen, lower alkoxy and lower alkyl.

5. The compound of claim 1 , wherein A is the group

6. The compound of claim 1 , wherein A is the group

7. The compound of claim 1 , wherein A is the group

wherein R 17 is hydrogen or CHF 2 .

8. The compound of claim 1 , wherein A is the group

9. The compound of claim 1 , wherein A is the group

10. The compound of claim 1 , wherein A is the group

11. The compound of claim 1 , wherein A is the group

12. The compound of claim 1 , wherein A is the group

wherein

R 18 -R 20 are each independently selected from hydrogen, lower alkyl or lower alkoxy.

13. The compound of claim 2 , selected from:

5-(3-chloro-4-fluoro-phenyl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

3-(2-methyl-imadazol-1-yl-methyl)-5-(3-trifluormethyl-phenyl)-pyridazine,

5-(3-difluormethyl-4-fluoro-phenyl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-[3-(1,1-difluoro-ethyl)-phenyl]-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-[3-(1,1-difluoro-ethyl)-4-fluoro-phenyl]-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-(4-fluoro-3-methyl-phenyl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-(4-chloro-3-methyl-phenyl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-[3-(1,1-difluoro-ethyl)-5-fluoro-phenyl]-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine,

5-(3-difluoromethyl-4-fluoro-phenyl)-3-(2-ethyl-imidazol-1-ylethyl)-pyridazine and

5-(3-cyclopropyl-4-fluoro-phenyl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine.

14. The compound of claim 5 , which is

5-benzo[b]thiophen-5-yl-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine.

15. The compound of claim 11 , which is

5-(3,4-dihydro-naphthalen-2-yl)-3-(2-methyl-imidazol-1-yl-methyl)-pyridazine hydrochloride.

16. A pharmaceutical composition comprising one or more compounds of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

17. A method of preparing a compound of formula I, claim 1 , comprising:

reacting a compound of formula

with a compound of formula

to give a compound of formula

18. A method of preparing a compound of formula I, claim 1 , comprising:

reacting a compound of formula

with a compound of formula

to obtain a compound of formula

19. A method of treating Alzheimer's disease comprising administering a therapeutically effective amount of a compound of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable acid addition salt thereof.

20. A method of treating Parkinson's disease comprising administering a therapeutically effective amount of a compound of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable acid addition salt thereof.

21. A method of treating ALS comprising administering a therapeutically effective amount of or compound of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable acid addition salt thereof.

22. A method of treating Huntingdon's disease comprising administering a therapeutically effective amount of a compound of formula

wherein

A is selected from:

and

R is hydrogen or lower alkyl;

or a pharmaceutically acceptable acid addition salt thereof.