Fused heterocyclic compounds

1. A method for treating obesity, drug addiction, or attention-deficit/hyperactivity disorder in a mammal, which comprises administering an effective amount of a compound represented by the formula (I) to the mammal:

wherein

ring A represents an optionally substituted 6-membered ring,

any one or two of from Z 1 to Z 4 represent —N═, and the others represent —CH═;

the nitrogen atom of —N═ for Z 1 to Z 4 may be oxidized;

Y represents an oxygen atom, a sulfur atom, an optionally substituted methylene group or —NR c —;

R c represents a hydrogen atom, or a substituent; and

R represents

(1) a group represented by the formula:

wherein

R 1 represents a phenyl group or 5- to 10-membered heterocyclic group, each of which is optionally substituted;

L represents a sulfur atom, an oxygen atom, an optionally substituted methylene group, —CO—, —NR a —, —CH 2 O—, —OCH 2 —, —NR a COO—, —OCONR a —, —NR a CONR b —, —NR a COCH 2 —, —CH 2 CONR a —, —NR a CO—, —CONR a —,

R a and R b are the same or different and each represents a hydrogen atom, or an optionally substituted C 1-6 alkyl group, or

L and R 1 in combination optionally form an optionally substituted bi- or tri-cyclic fused heterocyclic group; and

ring B 1 represents a benzene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring or a pyridazine ring, each of which is optionally substituted; or

(2) a group represented by the formula:

wherein

R 2 represents a phenyl group or 5- to 10-membered heterocyclic group, each of which is optionally substituted; and

the partial structure of the formula:

is

wherein

R x1 and R x2 are the same or different and each is a hydrogen atom or an optionally substituted C 1-6 alkyl group,

R x3 and R x5 are each a hydrogen atom or an optionally substituted C 1-6 alkyl group, and

the ring-constituting atom(s) of ring B 2 and ring D optionally further have substituent(s),

or a salt thereof.

2. The method according to claim 1 , wherein any one of Z 1 to Z 4 is —N═, and the others are —CH═.

3. The method according to claim 1 , wherein the partial structure of formula (I):

is a group represented by the formula:

wherein

Y 1 represents an optionally substituted methylene group or —NR c —,

R c represents a hydrogen atom, or a substituent, and

ring A 1 represents an optionally substituted pyridine ring, or

a group represented by the formula:

wherein

Y 2 represents —NR d —,

R d represents a substituent, and

ring A 2 represents an optionally substituted pyridine ring.

4. The method according to claim 1 , wherein L is an oxygen atom, or

—NR a — wherein R a represents a hydrogen atom or an optionally substituted C 1-6 alkyl group, or

L and R 1 in combination optionally form an optionally substituted bi- or tri-cyclic fused heterocyclic group.

5. The method according to claim 3 , wherein the partial structure of formula (I):

is a group represented by the formula:

wherein each symbol is as defined in claim 3 .

6. The method according to claim 3 , wherein the partial structure of formula (I):

is a group represented by the formula:

wherein

R 3 ′″ represents a hydrogen atom, a halogen atom, an optionally substituted C 1-4 alkyl group, or an optionally substituted C 1-4 alkoxy group, and

Y 1 is as defined in claim 3 .

7. The method according to claim 3 , wherein the partial structure of formula (I):

is a group represented by the formula:

wherein

R 3a and R 3b represent the same or different a hydrogen atom, a halogen atom, cyano, an optionally substituted C 1-4 alkyl group or an optionally substituted C 1-4 alkoxy group, and

R 4 represents an optionally substituted C 1-4 alkyl group,

provided that when one of R 3a and R 3b is a hydrogen atom, the other is not a hydrogen atom.

8. The method according to claim 1 , wherein ring B 1 is an optionally substituted benzene ring.

9. The method according to claim 1 , wherein R 1 is a 5- to 10-membered heterocyclic group which may be substituted.

10. The method according to claim 9 , wherein the 5- to 10-membered heterocyclic group which may be substituted is a group represented by the formula:

wherein R x represents a hydrogen atom or an optionally substituted C 1-6 alkyl group.

11. The method according to claim 1 , wherein the compound represented by formula (I) is 1-Ethyl-6-methyl-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

12. The method according to claim 1 , wherein the compound represented by formula (I) is 1-Ethyl-6-methoxy-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

13. The method according to claim 1 , wherein the compound represented by formula (I) is 1-Ethyl-7-methyl-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

14. The method according to claim 1 , wherein the compound represented by formula (I) is 6-Methyl-1-(1-methylethyl)-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

15. The method according to claim 1 , wherein the compound represented by formula (I) is 1-Ethyl-6-fluoro-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

16. The method according to claim 1 , wherein the compound represented by formula (I) is 1,7-Dimethyl-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.

17. The method according to claim 1 , wherein the compound represented by formula (I) is 1-Ethyl-7-(hydroxymethyl)-3-{4-[(3-methyl-3H-imidazo[4,5-b]pyridin-2-yl)oxy]phenyl}-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one.