Substituted imidazo[1,5-A] quinoxalines as a PDE9 inhibitor

A compound of the formula (I)

• wherein
• R1 is hydrogen,
• R2 is absent,
• R3 is C1-9 alkyl, C2-9 alkenyl or C2-9 alkynyl which are optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino group may further be substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, carbamoyl, oxo, carbocyclic or heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• aryl, saturated carbocyclic group or saturated heterocyclic group each of which is optionally substituted with halogen, hydroxy, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with halogen, hydroxy, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, carbocyclic group or heterocyclic group, independently of each other), C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, carbocyclic group or heterocyclic group;
• carboxy;
• C1-6 alkoxycarbonyl (wherein the C1-6 alkoxy moiety in the C1-6 alkoxycarbonyl may further be substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, amino, amido, carbamoyl, carbocyclic group or heterocyclic group);
• amido (wherein the amino moiety in the amido may further be substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group);
• or carbamoyl (wherein the amino moiety in the carbamoyl may further be substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group),
• R4 is hydrogen;
• hydroxy;
• C1-6 alkyl which is optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl or oxo;
• or amino which is optionally substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group,
• R5 and R8 each independently is hydrogen;
• halogen;
• C1-6 alkyl, C2-6 alkenyl or C1-6 alkoxy each of which is optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl or oxo;
• cyano;
• or nitro,
• R6 is halogen;
• C1-6 alkyl which is optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino may further be substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, carbamoyl, oxo, carbocyclic group or heterocyclic group (wherein the carbocyclic group and heterocyclic group may each be further substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• or COR9′, wherein R9′ is amino which may be substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group or heterocyclic group), C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• or aziridin-1-yl, azetidin-1-yl, pyrrolidin-1-yl, piperazin-1-yl, morpholin-1-yl or pyrazol-1-yl, each of which may be substituted with 1-2 substituents selected from the group consisting of hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group or heterocyclic group), C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino may further be substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, carbamoyl, oxo, carbocyclic group and heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl),
• R7 is hydrogen;
• halogen;
• C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl or C1-6 alkoxy each of which is optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino may further be substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, carbamoyl, oxo, carbocyclic group or heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• cyano;
• amino which is optionally substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl (wherein in the C1-6 alkyl, C2-6 alkenyl and C2-6 alkynyl may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, C1-6 alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group and heterocyclic group), alkanoyl, carbocyclic group and heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• carbocyclic group or heterocyclic group each of which is optionally substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, C1-6 alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group or heterocyclic group), C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl;
• COR9;
• or SO2R9,
• R9 is hydrogen;
• hydroxy;
• C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl or C1-6 alkoxy, each of which is optionally substituted with hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino may further be substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, oxo, carbocyclic group or heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• amino which may be substituted with 1-2 substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group or heterocyclic group), C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl);
• or aziridin-1-yl, azetidin-1-yl, pyrrolidin-1-yl, piperidin-1-yl, piperazin-1-yl, morpholin-1-yl or pyrazol-1-yl, each of which may be substituted with 1-2 substituents selected from hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy (wherein the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl and C1-6 alkoxy may further be substituted with, independently of each other, hydroxy, halogen, C1-6 alkoxy, C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino, amido, carbamoyl, oxo, carbocyclic group or heterocyclic group), C1-6 haloalkoxy having 1-9 halogen atoms, carboxy, C1-6 alkoxycarbonyl, alkanoyl, amino (wherein the amino may further be substituted with 1-2 substituents selected from the group consisting of C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl having 1-9 halogen atoms, alkanoyl, carbocyclic group and heterocyclic group), amido, carbamoyl, oxo, carbocyclic group and heterocyclic group (wherein the carbocyclic group and heterocyclic group each may further be substituted with hydroxy, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 alkoxy, carboxy, C1-6 alkoxycarbonyl, amino, amido or carbamoyl),
• X is S or O,
• A1 is C,
• A2 is N, and
• A3 is C,
• or a pharmaceutically acceptable salt thereof.