Imidazopyrazinones as PDE1 Inhibitors

Abstract

The present invention provides imidazopyrazinones as PDE1 inhibitors and their use as a medicament, in particular for the treatment of neurodegenerative disorders and psychiatric disorders.

What is claimed is: 
     
         1 . A compound according to formula (I) 
       
         
           
           
               
               
           
         
         wherein:
 n is 0 or 1; 
 q is 0 or 1; 
 R1 is selected from the group consisting of benzyl, indanyl, indoline and 5-membered heteroaryls; all of which can be substituted with a substituent selected from the group consisting of halogen and C 1 -C 3  alkyl; or 
 R1 is selected from the group consisting of saturated monocyclic rings containing 4-6 carbon atoms and 1-2 nitrogen atoms; all of which can be substituted one or more times with one or more substituents selected from the group consisting of methyl, fluorine and sulfonamide; or 
 R1 is selected from the group consisting of lactams containing 4-6 carbon atoms; all of which can be substituted one or more times with one or more substituents selected from the group consisting of methyl and fluorine; or 
 R1 is selected from the group consisting of bicyclic ethers such as, 7-oxabicyclo[2.2.1]heptane; all of which can be substituted one or more times with one or more substituents selected from the group consisting of methyl and fluorine; or 
 R1 is selected from the group consisting of linear or branched C 1 -C 8  alkyl, saturated monocyclic C 3 -C 8  cycloalkyl, oxetanyl, tetrahydrofuranyl and tetrathydropyranyl; all of which can be substituted one or more times with one or more substituents selected from the group consisting of methyl, fluorine, hydroxy, cyano or methoxy; or 
 R1 is a linear or branched C 1 -C 3  alkyl, which is substituted with a substituent selected from phenyl and 5-membered heteroaryl, wherein said 5-membered heteroaryl can be substituted with one or more C 1 -C 3  alkyls; or 
 R1 is selected from the group consisting of morpholine, tetrahydrofuran-3-amine, hexahydro-2H-furo[3,2-b]pyrrole and homomorpholine; all of which can be substituted with one or more substituents selected from the group consisting of C 1 -C 3  alkyl; 
 R2 is selected from the group consisting of hydrogen, linear or branched C 1 -C 8  alkyl, phenyl, saturated monocyclic C 3 -C 8  cycloalkyl, oxetanyl, benzo[d][1,3]dioxolyl, tetrahydrofuranyl and tetrahydropyranyl; or 
 R2 is phenyl or pyridyl substituted with one or more substituents selected from the group consisting of hydroxyl, amino, cyano, halogen, C 1 -C 3  alkyl, C 1 -C 3  alkoxy, C 3 -C 5  cycloalkoxy, C 3 -C 5  cycloalkyl-methoxy, C 1 -C 3  fluoroalkoxy, and —NC(O)CH 3 ; or 
 R2 is a 5-membered heteroaryl which can be substituted with one or more C 1 -C 3  alkyl; 
 R3 is selected from the group consisting of hydrogen, halogen, C 1 -C 5  alkyl, C 3 -C 5  cycloalkyl and phenyl; or 
 R3 is selected from the group consisting of phenyl substituted one or more times with C 1 -C 3  alkyl; methyl substituted one, two or three times with fluorine; ethyl substituted one, two or three times with fluorine; 
 R4 is hydrogen; 
 
         and tautomers and pharmaceutically acceptable addition salts thereof; 
         with the proviso that R2 and R3 cannot be hydrogen at the same time; 
         with the proviso, that the compound of formula (I) is not one of the three following compounds:
 3-methyl-7-(4-(trifluoromethoxy)benzyl)imidazo[1,5-a]pyrazin-8(7H)-one; 
 7-butyl-3-methylimidazo[1,5-a]pyrazin-8(7H)-one; and 
 7-(4-methoxybenzyl)-3-methylimidazo[1,5-a]pyrazin-8(7H)-one. 
 
       
     
     
         2 . The compound according to  claim 1 , wherein
 R1 is selected from the group consisting of linear or branched C 1 -C 8  alkyl, saturated monocyclic C 3 -C 8  cycloalkyl, oxetanyl, tetrahydrofuranyl, and tetrahydropyranyl;   R2 is selected from the group consisting of, linear or branched C 1 -C 8  alkyl, phenyl, and saturated monocyclic C 3 -C 8  cycloalkyl; or   R2 is selected from the group consisting of phenyl substituted with a substituent selected from the group consisting of halogen, C 1 -C 3  alkyl and methoxy;   R3 is selected from the group consisting of hydrogen, C 1 -C 3  alkyl, halogen and benzyl;   R4 is hydrogen.   
     
     
         3 . The compound of  claim 1 , wherein R1 is C 1 -C 3  alkyl. 
     
     
         4 . The compound of  claim 1 , wherein R1 is selected from tetrahydrofuranyl and tetrathydropyranyl. 
     
     
         5 . The compound of  claim 1 , wherein R1 is C 3 -C 5  cycloalkyl. 
     
     
         6 . The compound of  claim 1 , wherein R2 is C 1 -C 3  alkyl. 
     
     
         7 . The compound of  claim 1 , wherein R2 is phenyl. 
     
     
         8 . The compound of  claim 1 , wherein R2 is phenyl substituted with a substituent selected from the group consisting of fluorine, chlorine, methyl and methoxy. 
     
     
         9 . The compound of  claim 1 , wherein R2 is saturated monocyclic C 5 -C 7  cycloalkyl. 
     
     
         10 . The compound of  claim 1 , wherein R3 is selected from hydrogen, methyl, benzyl and bromine. 
     
     
         11 . The compound of  claim 1 , wherein R3 is selected from hydrogen and methyl; and wherein:
 R2 is selected from the group consisting of linear or branched C 1 -C 8  alkyl, phenyl, saturated monocyclic C 3 -C 8  cycloalkyl, oxetanyl, tetrahydrofuranyl and tetrahydropyranyl; or   R2 is phenyl or pyridyl substituted with one or more substituents selected from the group consisting of hydroxyl, amino, cyano, halogen, C 1 -C 3  alkyl, C 1 -C 3  alkoxy, C 1 -C 3  fluoroalkoxy, and —NC(O)CH 3 ; or   R2 is a 5-membered heteroaryl which can be substituted with C 1 -C 3  alkyl.   
     
     
         12 . The compound of  claim 1 , wherein the compound is selected from the group consisting of:
 (1) 7-(3-Fluorobenzyl)-3-propylimidazo[1,5-a]pyrazin-8(7H)-one;   (2) 6-Benzyl-7-(3-fluorobenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (3) 6-Benzyl-7-(cyclohexylmethyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (4) 7-(Cyclohexylmethyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (5) 7-(3-Fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (6) 3-Cyclopropyl-7-(3-fluorobenzyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (7) 7-(Cyclopentylmethyl)-3-cyclopropylimidazo[1,5-a]pyrazin-8(7H)-one;   (8) 7-(Cyclohexylmethyl)-3-cyclopropylimidazo[1,5-a]pyrazin-8(7H)-one;   (9) 7-(3-Fluorobenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (10) 7-(Cyclopentylmethyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (11) 7-(Cyclohexylmethyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (12) 7-(Cycloheptylmethyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (13) 7-(Cycloheptylmethyl)-3-cyclopropylimidazo[1,5-a]pyrazin-8(7H)-one;   (14) 7-(4-Chlorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (15) 6-Bromo-7-(3-fluorobenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (16) 7-Benzyl-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (17) 7-(2-Fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (18) 7-(3-Chlorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (19) 7-(2-Chlorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (20) 7-(3-Methoxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (21) 6-Methyl-7-(2-methylbenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (22) 6-Methyl-7-(4-methylbenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (23) 7-(4-Methoxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (24) 7-(4-Fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (25) 6-Methyl-7-(3-methylbenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (26) 7-(3-fluorobenzyl)-6-methyl-3-(4-methyltetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (27) 4-(7-(3-fluorobenzyl)-6-methyl-8-oxo-7,8-dihydroimidazo[1,5-a]pyrazin-3-yl)tetrahydro-2H-pyran-4-carbonitrile;   (28) 7-(3-fluorobenzyl)-3-(4-methoxytetrahydro-2H-pyran-4-yl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (29) 7-(3-fluorobenzyl)-3-(4-fluorotetrahydro-2H-pyran-4-yl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (30) (R)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-2-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and
 (S)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-2-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (31) (R)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and
 (S)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (32) (R)-7-(3-fluorobenzyl)-6-methyl-3-(3-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and
 (S)-7-(3-fluorobenzyl)-6-methyl-3-(3-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (33) 7-(3-fluorobenzyl)-6-methyl-3-(1-methylcyclopropyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (34) 3-(2,2-difluorocyclopropyl)-7-(3-fluorobenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (35) 7-(3-fluorobenzyl)-6-methyl-3-((1R,2S)-2-methylcyclopropyl)imidazo[1,5-a]pyrazin-8(7H)-one;
 7-(3-fluorobenzyl)-6-methyl-3-((1R,2R)-2-methylcyclopropyl)imidazo[1,5-a]pyrazin-8(7H)-one; 
 7-(3-fluorobenzyl)-6-methyl-3-((1S,2S)-2-methylcyclopropyl)imidazo[1,5-a]pyrazin-8(7H)-one; and 
 7-(3-fluorobenzyl)-6-methyl-3-((1S,2R)-2-methylcyclopropyl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (36) 7-(3-fluorobenzyl)-6-methyl-3-((2S,3R)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one;
 7-(3-fluorobenzyl)-6-methyl-3-((2S,3S)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
 7-(3-fluorobenzyl)-6-methyl-3-((2R,3R)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and 
 7-(3-fluorobenzyl)-6-methyl-3-((2R,3S)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (37) 7-(3-fluorobenzyl)-3-((1R,2S)-2-fluorocyclopropyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; and
 7-(3-fluorobenzyl)-3-((1R,2R)-2-fluorocyclopropyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; 
   (38) 7-(3-fluorobenzyl)-3-((1S,2S)-2-fluorocyclopropyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; and
 7-(3-fluorobenzyl)-3-((1S,2R)-2-fluorocyclopropyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; 
   (39) 7-(4-cyclopropoxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (40) 7-(4-(difluoromethoxy)benzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (41) 6-methyl-3-(tetrahydro-2H-pyran-4-yl)-7-(4-(trifluoromethoxy)benzyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (42) 7-(4-(cyclopropylmethoxy)benzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (43) 7-benzyl-6-ethyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (44) 6-ethyl-7-(4-methoxybenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (45) 3-((6-methyl-8-oxo-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-7(8H)-yl)methyl)benzonitrile;   (46) 4-((6-methyl-8-oxo-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-7(8H)-yl)methyl)benzonitrile;   (47) N-(4-((6-methyl-8-oxo-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-7(8H)-yl)methyl)phenyl)acetamide;   (48) 7-(4-chloro-3-methoxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (49) 7-(2-ethylbenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (50) 7-(benzo[d][1,3]dioxol-5-ylmethyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (51) 7-(3-chloro-4-methoxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (52) 7-(4-aminobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (53) 7-(4-hydroxybenzyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (54) 6-ethyl-7-(3-fluorobenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (55) 7-(4-methoxybenzyl)-6-methyl-3-((2S,3R)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one;
 7-(4-methoxybenzyl)-6-methyl-3-((2S,3S)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
 7-(4-methoxybenzyl)-6-methyl-3-((2R,3R)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and 
 7-(4-methoxybenzyl)-6-methyl-3-((2R,3S)-2-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (56) 7-(4-methoxybenzyl)-6-methyl-3-propylimidazo[1,5-a]pyrazin-8(7H)-one;   (57) 7-((6-methoxypyridin-3-yl)methyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (58) 6,7-dimethyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (59) 7-ethyl-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (60) 6-methyl-7-propyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (61) 7-isopropyl-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (62) 7-isopentyl-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (63) 7-(cyclopentylmethyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (64) 2-((6-methyl-8-oxo-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-7(8H)-yl)methyl)benzonitrile;   (65) 7-(cycloheptylmethyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (66) 6-methyl-7-(((trans)-4-methylcyclohexyl)methyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one; and
 6-methyl-7-(((cis)-4-methylcyclohexyl)methyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   (67) 7-(((cis)-4-methoxycyclohexyl)methyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (68) 7-(((trans)-4-methoxycyclohexyl)methyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (69) 7-(4-methoxybenzyl)-6-methyl-3-(3-methyltetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (70) 7-(4-methoxybenzyl)-6-methyl-3-((1R,2R,4S)-2-methyl-7-oxabicyclo[2.2.1]heptan-2-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (71) (S)-7-(4-methoxybenzyl)-6-methyl-3-(1-phenylethyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (72) (R)-7-(4-methoxybenzyl)-6-methyl-3-(1-phenylethyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (73) 3-(1,4-dimethylpiperidin-4-yl)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (74) 3-(6-chloro-2,3-dihydro-1H-inden-1-yl)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (75) 7-(4-methoxybenzyl)-6-methyl-3-(3-methyl-5-oxopyrrolidin-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (76) 3-(1-methoxy-2-methylpropan-2-yl)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (77) 3-isopropyl-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (78) 6-methyl-7-((2-methylthiazol-4-yl)methyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (79) 6-methyl-3-(tetrahydro-2H-pyran-4-yl)-7-(thiophen-3-ylmethyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (80) 6-methyl-3-(tetrahydro-2H-pyran-4-yl)-7-(thiazol-4-ylmethyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (81) 7-((3,5-dimethylisoxazol-4-yl)methyl)-6-methyl-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (82) 6-methyl-7-((5-methylisoxazol-3-yl)methyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (83) 6-methyl-7-((3-methylisoxazol-5-yl)methyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (84) 3-(2,6-dimethyltetrahydro-2H-pyran-4-yl)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (85) 7-(cyclohexylmethyl)-6-methyl-3-propylimidazo[1,5-a]pyrazin-8(7H)-one;   (86) 3-(2-hydroxypropan-2-yl)-7-(4-methoxybenzyl)-6-methyl imidazo[1,5-a]pyrazin-8(7H)-one;   (87) 3-(2-fluoropropan-2-yl)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (88) 7-(4-methoxybenzyl)-6-methyl-3-(7-oxoazepan-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (89) 7-(4-methoxybenzyl)-6-methyl-3-(5-methyltetrahydrofuran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (90) 7-(4-methoxybenzyl)-6-methyl-3-(1-(4-methylthiazol-2-yl)ethyl)imidazo[1,5-a]pyrazin-8(7H)-one;   (91) 3-(7-(4-methoxybenzyl)-6-methyl-8-oxo-7,8-dihydroimidazo[1,5-a]pyrazin-3-yl)-3-methylpyrrolidine-1-sulfonamide;   (92) 6-(cyclopentylmethyl)-7-(4-methoxybenzyl)-3-(tetrahydro-2H-pyran-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (93) 3-(morpholino)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (94) 7-(4-methoxybenzyl)-6-methyl-3-((tetrahydrofuran-3-yl)amino)imidazo[1,5-a]pyrazin-8(7H)-one;   (95) (R)-7-(4-methoxybenzyl)-6-methyl-3-(3-methyl morpholino)imidazo[1,5-a]pyrazin-8(7H)-one;   (96) (S)-7-(4-methoxybenzyl)-6-methyl-3-(3-methylmorpholino)imidazo[1,5-a]pyrazin-8(7H)-one;   (97) 7-(4-methoxybenzyl)-6-methyl-3-(1,4-oxazepan-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one;   (98) 3-(2,2-dimethylmorpholino)-7-(4-methoxybenzyl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one;   (99) 7-(3-fluorobenzyl)-3-((3aS,6aS)-hexahydro-4H-furo[3,2-b]pyrrol-4-yl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; and
 7-(3-fluorobenzyl)-3-((3aR,6aR)-hexahydro-4H-furo[3,2-b]pyrrol-4-yl)-6-methylimidazo[1,5-a]pyrazin-8(7H)-one; 
   (100) (R)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-3-yl) imidazo[1,5-a]pyrazin-8(7H)-one; and
 (S)-7-(3-fluorobenzyl)-6-methyl-3-(tetrahydro-2H-pyran-3-yl)imidazo[1,5-a]pyrazin-8(7H)-one; 
   and pharmaceutically acceptable salts of any of these compounds.   
     
     
         13 . A pharmaceutical composition comprising a therapeutically effective amount of the compound of  claim 1  and one or more pharmaceutically acceptable carriers, diluents and excipients. 
     
     
         14 . A pharmaceutical composition comprising a therapeutically effective amount of the compound of  claim 2  and one or more pharmaceutically acceptable carriers, diluents and excipients 
     
     
         15 . A pharmaceutical composition comprising a therapeutically effective amount of the compound of  claim 11  and one or more pharmaceutically acceptable carriers, diluents and excipients 
     
     
         16 . A pharmaceutical composition comprising a therapeutically effective amount of the compound of  claim 12  and one or more pharmaceutically acceptable carriers, diluents and excipients 
     
     
         17 . A method for the treatment of a neurodegenerative disorder, selected from the group consisting of Alzheimer's Disease, Parkinson's Disease and Huntington's Disease or for the treatment of a psychiatric disorder such as Attention Deficit Hyperactivity Disorder (ADHD), depression, anxiety, narcolepsy, cognitive impairment and cognitive impairment associated with schizophrenia (CIAS), or another brain disease like restless leg syndrome, wherein said method comprises administering a therapeutically effective amount of the compound of  claim 1  to a subject in need thereof. 
     
     
         18 . A method for the treatment of a neurodegenerative disorder, selected from the group consisting of Alzheimer's Disease, Parkinson's Disease and Huntington's Disease or for the treatment of a psychiatric disorder such as Attention Deficit Hyperactivity Disorder (ADHD), depression, anxiety, narcolepsy, cognitive impairment and cognitive impairment associated with schizophrenia (CIAS), or another brain disease like restless leg syndrome, wherein said method comprises administering a therapeutically effective amount of the compound of  claim 2  to a subject in need thereof. 
     
     
         19 . A method for the treatment of a neurodegenerative disorder, selected from the group consisting of Alzheimer's Disease, Parkinson's Disease and Huntington's Disease or for the treatment of a psychiatric disorder such as Attention Deficit Hyperactivity Disorder (ADHD), depression, anxiety, narcolepsy, cognitive impairment and cognitive impairment associated with schizophrenia (CIAS), or another brain disease like restless leg syndrome, wherein said method comprises administering a therapeutically effective amount of the compound of  claim 11  to a subject in need thereof. 
     
     
         20 . A method for the treatment of a neurodegenerative disorder, selected from the group consisting of Alzheimer's Disease, Parkinson's Disease and Huntington's Disease or for the treatment of a psychiatric disorder such as Attention Deficit Hyperactivity Disorder (ADHD), depression, anxiety, narcolepsy, cognitive impairment and cognitive impairment associated with schizophrenia (CIAS), or another brain disease like restless leg syndrome, wherein said method comprises administering a therapeutically effective amount of the compound of  claim 12  to a subject in need thereof.