Piperidine compounds for use as orexin receptor antagonist

1. A compound of formula (I):

wherein:

X is a bond,

Y is CH 2 , CHOH, or —CH 2 CH(OH)—;

Het is optionally substituted 1,3,4-oxadiazolyl;

Ar 2 represents an optionally substituted phenyl, wherein the phenyl is substituted by R 1 and is further optionally substituted;

R 1 is hydrogen, an optionally substituted (C 1-4 )alkoxy, halo, cyano, optionally substituted(C 1-6 )alkyl, or optionally substituted phenyl;

wherein said optionally substituted oxadiazolyl, (C 1-4 )alkoxy, (C 1-6 )alkyl, or phenyl is optionally substituted by halogen, hydroxy, oxo, cyano, nitro, (C 1-4 )alkyl, (C 1-4 )alkoxy, hydroxy(C 1-4 )alkyl, hydroxy(C 1-4 )alkoxy, halo(C 1-4 )alkyl, halo(C 1-4 )alkoxy, aryl(C 1-4 )alkoxy, (C 1-4 )alkylthio, hydroxy(C 1-4 alkyl, (C 1-4 )alkoxy(C 1-4 )alkyl, (C 3-6 )cycloalkyl(C 1-4 )alkoxy, (C 1-4 )alkanoyl, (C 1-4 )alkoxycarbonyl, (C 1-4 )alkylsulfonyl, (C 1-4 )alkylsulfonyloxy, (C 1-4 )alkylsulfonyl(C 1-4 )alkyl, arylsulfonyl, arylsulfonyloxy, arylsulfonyl(C 1-4 )alkyl, (C 1-4 )alkylsulfonamido, (C 1-4 )alkylamido, (C 1-4 )alkylsulfonamido(C 1-4 )alkyl, (C 1-4 )alkylamido(C 1-4 )alkyl, arylsulfonamido, arylcarboxamido, arylsulfonamido(C 1-4 )alkyl, arylcarboxamido(C 1-4 )alkyl, aroyl, aroyl(C 1-4 )alkyl, aryl(C 1-4 )alkanoyl, (C 1-4 )acyl, aryl, arykC 1-4 )alkyl, (C 1-4 )alkylamino(C 1-4 )alkyl, R a R b N—, R a OCO(CH 2 ) r , R a CON(R a )(CH 2 ) r , R a R b NCO(CH 2 ) r , R a R b NSO 2 (CH 2 ) r or R a SO 2 NR b (CH 2 ) r , wherein r represents zero or an integer from 1 to 4, or R a R b N(CH 2 )n- or R a R b N(CH 2 )nO—, wherein n represents an integer from 1 to 4, wherein each of R a and R b independently represents a hydrogen atom or a (C 1-4 )alkyl group;

or a pharmaceutically acceptable salt thereof.

2. A compound according to claim 1 , wherein R 1 represents an optionally substituted phenyl group.

3. A compound according to claim 1 , wherein Y is CH 2 .

4. A compound according to claim 1 , wherein optional substituents for said optionally substituted (C 1-4 )alkoxy, (C 1-6 )alkyl or phenyl of R 1 are halogen, (C 1-4 )alkoxy(C 1-4 )alkyl, R a R b N, R a R b N(CH 2 )n, R a R b N(CH 2 )nO, (C 1-4 )alkoxy, (C 1-4 )alkanoyl and (C 1-4 )alkyl.

5. A pharmaceutical composition comprising the compound of formula (I), or the pharmaceutically acceptable salt thereof, according to claim 1 , and a pharmaceutically acceptable carrier.

6. A method of treating a disease or disorder where an antagonist of a human orexin receptor is required, which comprises administering to a subject in need thereof an effective amount of the compound, or the pharmaceutically acceptable salt thereof, according to claim 1 , wherein said disease or disorder is selected from insomnia, parasomnia and jet-lag syndrome.

7. A method according to claim 6 , wherein said disease or disorder is insomnia.

8. A method of treating a disease or disorder where an antagonist of a human orexin receptor is required, which comprises administering to a subject in need thereof an effective amount of the compound, or the pharmaceutically acceptable salt thereof, according to claim 1 , wherein said disease or disorder is selected from obesity and obesity associated with Type II diabetes.