Substituted cyclopentanes, tetrahydrofuranes and pyrrolidines as orexin receptor antagonists

1. A compound of formula

wherein

R 1 represents an 8- to 10-membered fused bicyclic heteroaromatic group optionally substituted by at least one substituent independently selected from halogen, cyano, hydroxyl, C 3 -C 6 cycloalkyl, C 1 -C 3 alkyl, C 1 -C 3 alkoxy, C 1 -C 3 alkoxycarbonyl, C 1 -C 3 alkoxycarbonylamino, C 1 -C 3 haloalkoxy, —NR 4 R 5 , C 3 -C 6 cycloalkylamino, C 1 -C 3 alkylcarbonyloxy, C 1 -C 3 alkylcarbonylamino, sulphonamido, C 1 -C 3 alkylsulphonyl, C 1 -C 3 alkylsulphonylamino and —C(O)NR 6 R 7 ;

L represents a bond, CH 2 , O, NH or N(CH 3 );

R a represents a hydrogen atom or a C 1 -C 3 alkyl or C 1 -C 3 haloalkyl group;

R b represents a hydrogen atom or a C 1 -C 3 alkyl or C 1 -C 3 haloalkyl group;

X represents CF 2 , CHR 8 ;

R 2 represents a hydrogen atom or a C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl group;

R 3 represents a 5- or 6-membered monocyclic heteroaromatic group optionally substituted by at least one substituent independently selected from halogen, hydroxyl, cyano, C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, C 1 -C 3 hydroxyalkyl, C 1 -C 3 alkoxy, C 1 -C 3 haloalkoxy, C 2 -C 4 alkenyl, C 1 -C 3 alkylcarbonyloxy, C 1 -C 3 alkoxycarbonyl, —NR 10 R 11 , —C(O)NR 12 R 13 , C 3 -C 6 cycloalkyl, C 3 -C 6 cycloalkyloxy, C 3 -C 6 cycloalkylmethyl or a 5- or 6-membered heteroaryl group, the heteroaryl group being optionally substituted by at least one substituent independently selected from C 1 -C 6 alkyl, C 1 -C 6 alkoxy and C 1 -C 6 haloalkoxy;

R 4 and R 5 each independently represent a hydrogen atom or a C 1 -C 3 alkyl or C 3 -C 6 cycloalkyl group, or R 4 and R 5 may together with the nitrogen atom to which they are attached form a 4- to 7-membered saturated heterocyclic ring optionally substituted by at least one substituent independently selected from halogen, hydroxyl and C 1 -C 3 alkoxy;

R 6 and R 7 each independently represent a hydrogen atom or a C 1 -C 3 alkyl or C 3 -C 6 cycloalkyl group, or R 6 and R 7 may together with the nitrogen atom to which they are attached form a 4- to 7-membered saturated heterocyclic ring optionally substituted by at least one substituent independently selected from halogen and hydroxyl;

R 8 represents a hydrogen or halogen atom or a hydroxyl group;

R 10 and R 11 each independently represent a hydrogen atom or a C 1 -C 3 alkyl or C 3 -C 6 cycloalkyl group, or R 10 and R 11 may together with the nitrogen atom to which they are attached form a 4- to 7-membered saturated heterocyclic ring optionally substituted by at least one substituent independently selected from halogen, hydroxyl and C 1 -C 3 alkoxy; and

R 12 and R 13 each independently represent a hydrogen atom or a C 1 -C 3 alkyl or C 3 -C 6 cycloalkyl group, or R 12 and R 13 may together with the nitrogen atom to which they are attached form a 4- to 7-membered saturated heterocyclic ring optionally substituted by at least one substituent independently selected from halogen and hydroxyl;

or a pharmaceutically acceptable salt thereof.

2. A compound according to claim 1 , wherein R 1 represents a 9- or 10-membered fused bicyclic heteroaromatic group containing one or two ring heteroatoms independently selected from nitrogen, oxygen and sulphur, the heteroaromatic group being optionally substituted by one or more halogen atoms.

3. A compound according to claim 1 , wherein R 1 represents a 9- or 10-membered fused bicyclic heteroaromatic group selected from quinoxalinyl, benzothiazolyl, benzoxazolyl, quinolinyl and quinazolinyl, all optionally substituted as claimed in claim 1 .

4. A compound according to claim 1 , wherein X represents CH 2 .

5. A compound according to claim 1 , wherein L represents NH.

6. A compound according to claim 1 , wherein R 2 represents a hydrogen atom or methyl group.

7. A compound according to claim 1 , wherein R 3 represents a 5- or 6-membered monocyclic heteroaromatic group selected from pyridinyl, pyrimidinyl and pyrazinyl, all optionally substituted as claimed in claim 1 .

8. A compound according to claim 1 , wherein R 3 is optionally substituted by at least one substituent independently selected from fluorine, chlorine, bromine, C 1 -C 3 alkyl, C 1 -C 3 alkoxy, C 1 -C 3 haloalkyl, C 1 -C 3 haloalkoxy, —NR 10 R 11 , or a 5- or 6-membered heteroaryl group, the heteroaryl group being optionally substituted by one or two substituents independently selected from C 1 -C 2 alkyl, C 1 -C 2 alkoxy and C 1 -C 2 haloalkoxy.

9. A compound according to claim 1 , wherein R 3 is optionally substituted by at least one 5- or 6-membered heteroaryl group selected from triazolyl, pyrazolyl, oxadiazolyl, pyrimidinyl and imidazolyl, all optionally substituted by one or two substituents independently selected from C 1 -C 2 alkyl.

10. A compound of formula (I) as claimed in claim 1 selected from the group consisting of:

3-Bromo-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino] cyclopentyl]-pyridine-2-carboxamide;

6-Bromo-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino] cyclopentyl]-3-methoxypyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-methoxypyridine-2-carboxamide;

3-Chloro-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino] cyclopentyl]-pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-methoxy-N-methylpyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(2H-1,2,3-triazol-2-yl)pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzoxazol-2-yl)amino]cyclopentyl]-3-methoxypyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(propan-2-yloxy)pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-methoxy-6-methylpyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(1H-pyrazol-1-yl)pyridine-2-carboxamide;

3-Fluoro-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(piperidin-1-yl)pyridine-2-carboxamide;

3-(Azetidin-1-yl)-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(pyrrolidin-1-yl)pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(3-methoxyazetidin-1-yl)pyridine-2-carboxamide;

3-Methoxy-N-[(1S,2S)-2-[(quinoxalin-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-methoxy-6-(trifluoromethyl)pyridine-2-carboxamide;

3-Ethoxy-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(trifluoromethoxy)pyridine-2-carboxamide;

3-(Difluoromethoxy)-N-[(1S,2S)-2-[(6-fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Chloro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(2H-1,2,3-triazol-2-yl)pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Chloro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(difluoromethoxy)pyridine-2-carboxamide;

3-(Difluoromethoxy)-N-[(1S,2S)-2-[(6-fluoro-1,3-benzoxazol-2-yl)amino]cyclopentyl]pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Fluoro-1,3-benzothiazol-2-yl)amino]cyclopentyl]-3-(1H-1,2,3-triazol-1-yl)pyridine-2-carboxamide;

N-[(1S,2S)-2-[(6-Chloro-1,3-benzoxazol-2-yl)amino]cyclopentyl]-3-(difluoromethoxy)pyridine-2-carboxamide;

3-Ethoxy-6-methyl-N-[2-(quinolin-2-ylmethyl)cyclopentyl]pyridine-2-carboxamide;

3-Ethoxy-6-methyl-N-[2-(quinolin-2-ylmethyl)cyclopentyl]pyridine-2-carboxamide;

enantiomers thereof and pharmaceutically acceptable salts of any of the foregoing.

11. A pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof as claimed in claim 1 , in association with a pharmaceutically acceptable adjuvant, diluent or carrier, and optionally one or more other therapeutic agents.

12. A composition according to claim 11 , wherein the one or more other therapeutic agents are selected from carbamazepine, olanzapine, quetiapine, verapamil, lamotrigine, oxcarbazepine, risperidone, aripiprazole, ziprasidone and lithium.