N-acyl-(3-substituted)-(8-substituted)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazines as selective NK-3 receptor antagonists

1. A method for treating and/or preventing polycystic ovary syndrome in a patient, comprising administering to a patient in need thereof a pharmaceutically effective amount of a compound of Formula I:

wherein:

R 1 is H, F, or methyl;

R 1′ is H;

R 2 is H, F, Cl, or methoxy;

R 2′ is H or F;

R 3 is H, F, Cl, methyl, trifluoromethyl, or cyano;

R 4 is methyl, ethyl, n-propyl, hydroxyethyl, methoxyethyl, trifluoromethyl, difluoromethyl, or fluoromethyl;

R 5 is methyl, ethyl, methoxymethyl, trifluoromethyl, difluoromethyl, or fluoromethyl;

X 1 is N and X 2 is S or O; or X 1 is S and X 2 is N;

represents a single or a double bond depending on X 1 and X 2 ; and

stands for the (R)-enantiomer or for the racemate of the compound of Formula I.

2. The method according to claim 1 , wherein the compound is of Formula Ia:

3. The method according to claim 1 , wherein the compound is of Formula Ia-1:

4. The method according to claim 1 , wherein the compound is of Formula Ia-2:

5. The method according to claim 1 , wherein the compound is of Formula Ia-3:

6. The method according to claim 1 , wherein the compound is of Formula Ib:

wherein:

R 3 is F; and

R 5 is methyl, ethyl, trifluoromethyl, difluoromethyl, or fluoromethyl.

7. The method according to claim 1 , wherein the compound is of Formula Ic:

wherein:

R 4 is methyl, ethyl, n-propyl, or hydroxyethyl;

R 5 is methyl, ethyl, or trifluoromethyl.

8. The method according to claim 1 , wherein the compound is selected from the group consisting of:

(R)-(3,4-dichlorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3-(3-ethyl-1,2,4-thiadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(R)-(4-chlorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(4-chloro-3-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3-chloro-4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(3,4,5-trifluorophenyl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(2,3,4-trifluorophenyl)methanone;

(R)-(3,4-difluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(2,3,4,5-tetrafluorophenyl)methanone;

(R)-(4-fluorophenyl)(8-(2-hydroxyethyl)-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(4-fluorophenyl)(8-(2-hydroxyethyl)-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3-(3-ethyl-1,2,4-oxadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3-chlorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(3,5-difluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(2,4-difluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(p-tolyl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(phenyl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-(trifluoromethyl)phenyl)methanone;

(R)-(8-ethyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(8-ethyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(R)-(4-fluorophenyl)(3-(3-methyl-1,2,4-thiadiazol-5-yl)-8-propyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(4-fluoro-3-methoxyphenyl) (8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(o-tolyl)methanone;

(R)-(3-methoxyphenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-oxadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-4-(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine-7-carbonyl)benzonitrile;

(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(2,3,4,5-tetrafluorophenyl)methanone;

(3,4-difluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(2,3,4-trifluorophenyl)methanone;

(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(3,4,5-trifluorophenyl)methanone;

(3-chloro-4-fluorophenyl)(8-methyl-3-(3-methyl-, 2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(4-chloro-3-fluorophenyl)(8-methyl-3-(3-methyl-, 2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(4-chlorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(3,4-dichlorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(3-(3-ethyl-1,2,4-thiadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(3-(3-ethyl-1,2,4-oxadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(R)-(4-fluorophenyl)(8-methyl-3-(3-(trifluoromethyl)-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone; and

(R)-(3-(3-(difluoromethyl)-1,2,4-thiadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone.

9. The method according to claim 1 , wherein the compound is selected from the group consisting of:

(R)-(3-(3-ethyl-1,2,4-thiadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl) (4-fluorophenyl)methanone;

(R)-(4-chlorophenyl) (8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(R)-(4-fluorophenyl) (8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone;

(4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone; and

(R)-(4-fluorophenyl) (8-methyl-3-(3-methyl-1,2,4-oxadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone.

10. The method according to claim 1 ,

wherein the compound is (R)-(4-fluorophenyl)(8-methyl-3-(3-methyl-1,2,4-thiadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone.

11. A method for treating and/or preventing polycystic ovary syndrome in a patient, comprising administering to a patient in need thereof a pharmaceutically effective amount of a compound of Formula I:

wherein:

R 1 is H, F, or methyl;

R 1′ is H;

R 2 is H, F, Cl, or methoxy;

R 2′ is H or F;

R 3 is H, F, Cl, methyl, trifluoromethyl, or cyano;

R 4 is methyl, ethyl, n-propyl, hydroxyethyl, methoxyethyl, trifluoromethyl, difluoromethyl, or fluoromethyl;

R 5 is 1-fluoroethyl, 1,1-difluoroethyl, or 2,2,2-trifluoroethyl;

X 1 is N and X 2 is S or O; or X 1 is S and X 2 is N;

represents a single or a double bond depending on X 1 and X 2 ; and

stands for the (R)-enantiomer or for the racemate of the compound of Formula I.

12. The method according to claim 11 , wherein the compound is of Formula Ib:

R 3 is F.

13. The method according to claim 11 , wherein the compound is selected from the group consisting of:

(R)-(3-(3-(1,1-difluoroethyl)-1,2,4-oxadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)(4-fluorophenyl)methanone;

(R)-(4-fluorophenyl)(8-methyl-3-(3-(2,2,2-trifluoroethyl)-1,2,4-oxadiazol-5-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone; and

(8R)-3-(3-(1-fluoroethyl)-1,2,4-oxadiazol-5-yl)-8-methyl-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl) (4-fluorophenyl)methanone.