Claims
[Claim 1] A compound of the formula (I) or a salt thereof:
[Chem. 1]
(in the formula,
R1, R2, and R3 are the same as or different from each other, and are H, halogen, lower alkyl, or halo-lower alkyl;
R4 is H, halogen, lower alkyl, or halo-lower alkyl;
R5 is H;
R6 is phenyl which may be substituted; or
R5 and R6 may form a benzene ring which may be substituted, together with carbon atoms to which they are bonded; and
— is a single bond or a double bond.)
[Claim 2] The compound or a salt thereof according to claim 1, wherein R5 is H, and
R6 is phenyl which may be substituted.
[Claim 3] The compound or a salt thereof according to claim 2, wherein ^^ is a
single bond.
[Claim 4] The compound or a salt thereof according to claim 3, wherein R4 is H.
[Claim 5] The compound or a salt thereof according to claim 4, wherein R1 is H, R2
is H or halogen, and R3 is halogen.
[Claim 6] The compound or a salt thereof according to claim 5, wherein R6 is phenyl
which may be substituted with one to four RA1's which are the same as or different from each other, and

RA1
is a group selected from the group consisting of -OH, -O-lower alkyl, -CN, halogen, lower alkyl, halo-lower alkyl, lower alkylene-O-lower alkyl, -C(=0)-lower alkyl, and -C(=0)-lower alkylene-CN.
[Claim 7] The compound or a salt thereof according to claim 6, wherein R6 is phenyl
which may be substituted with one R^, and
R^ is a group selected from the group consisting of halogen, lower alkyl, and halo-lower alkyl.
[Claim 8] The compound or a salt thereof according to claim 7, wherein R2 is H.
[Claim 9] The compound or a salt thereof according to claim 8, wherein R6 is phenyl
which may be substituted with one R^ at a para-position from its bond.
[Claim 10] The compound or a salt thereof according to claim 1, wherein the
compound is selected from the group consisting of:
4-fluoro-3-(2-oxo-2-{2-[4-(trifluoromethyl)phenyl]-6,7-dihydro-5H-imidazo[ 1,2-a][l,4]diazepin-8(9H)-yl}ethyl)-l,3-benzoxazol-2(3H)-one,
4-fluoro-3-{2-[2-(2-fluorophenyl)-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl]-2-oxoethyl}-l,3-benzoxazol-2(3H)-one,
3 - [2-(4,5 -dihydro-1H- [ 1,4] diazepino [ 1,2-a]benzimidazol-2(3 H)-yl)-2-oxoethyl] -4,5-difluoro-l,3-benzoxazol-2(3H)-one,
4-fluoro-3-[2-(8-fluoro-4,5-dihydro-lH-[l,4]diazepino[l,2-a]benzimidazol-2(3H)-yl)-2-oxoethyl]-l,3-benzoxazol-2(3H)-one,
4,5-difluoro-3-[2-oxo-2-(2-phenyl-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl)ethyl]-l,3-benzoxazol-2(3H)-one,
4-fluoro-3 - { 2- [2-(3 -fluorophenyl)-6,7-dihydro-5H-imidazo [ 1,2-a] [ 1,4] diazepin-8(9H)-yl]-2-oxoethyl}-l,3-benzoxazol-2(3H)-one, and
3-{2-[2-(4-chlorophenyl)-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl]-2-oxoethyl}-4-fluoro-l,3-benzoxazol-2(3H)-one.
[Claim 11]
The compound or a salt thereof according to claim 10, wherein the compound is selected from the group consisting of:
4-fluoro-3-(2-oxo-2-{2-[4-(trifluoromethyl)phenyl]-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl}ethyl)-l,3-benzoxazol-2(3H)-one,
4-fluoro-3-{2-[2-(2-fluorophenyl)-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl]-2-oxoethyl}-l,3-benzoxazol-2(3H)-one,

4,5-difluoro-3-[2-oxo-2-(2-phenyl-6,7-dihydro-5H-imidazo[l ,2-a] [1,4]diazepin-8(9H)-yl)ethyl]-l,3-benzoxazol-2(3H)-one,
4-fluoro-3-{2-[2-(3-fluorophenyl)-6,7-dihydro-5H-imidazo[l52-a][l,4]diazepin-8(9H)-yl]-2-oxoethyl}-l,3-benzoxazol-2(3H)-one, and
3-{2-[2-(4-chlorophenyl)-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl]-2-oxoethyl}-4-fluoro-l,3-benzoxazol-2(3H)-one.
[Claim 12] The compound or a salt thereof according to claim 10, wherein the
compound is 4-fluoro-3-(2-oxo-2-{2-[4-(trifluoromethyl)phenyl]-6,7-dihydro-5H-imidazo[l,2-a][l,4]diazepin-8(9H)-yl}ethyl)-l,3-benzoxazol-2(3H)-one.
[Claim 13] The compound or a salt thereof according to claim 10, wherein the
compound is 3-{2-[2-(4-chlorophenyl)-6,7-dihydro-5H-imidazo[l,2-a][1,4]diazepin-8(9H)-yl]-2-oxoethyl}-4-fluoro-l,3-benzoxazol-2(3H)-one.
[Claim 14] A pharmaceutical composition comprising the compound or a salt thereof
according to claim 1 and a pharmaceutically acceptable excipient.
[Claim 15] The pharmaceutical composition according to claim 14, which is a
dopamine Dl receptor positive allosteric modulator.
[Claim 16] The pharmaceutical composition according to claim 14, which is a
pharmaceutical composition for preventing and/or treating cognitive impairment, schizophrenia negative symptom, cognitive impairment associated with schizophrenia (CIAS), Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, attention deficit hyperactivity disorder (ADHD), or drug dependency.
[Claim 17] Use of the compound or a salt thereof according to claim 1 for the
manufacture of a pharmaceutical composition for preventing and/or treating cognitive impairment, schizophrenia negative symptom, cognitive impairment associated with schizophrenia (CIAS), Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, attention deficit hyperactivity disorder (ADHD), or drug dependency.
[Claim 18] Use of the compound or a salt thereof according to claim 1 for preventing
and/or treating cognitive impairment, schizophrenia negative symptom, cognitive impairment associated with schizophrenia (CIAS), Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, attention deficit hyperactivity disorder (ADHD), or drug dependency.

[Claim 19] The compound or a salt thereof according to claim 1 for preventing and/or
treating cognitive impairment, schizophrenia negative symptom, cognitive impairment associated with schizophrenia (CIAS), Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, attention deficit hyperactivity disorder (ADHD), or drug dependency.
[Claim 20] A method for preventing and/or treating cognitive impairment,
schizophrenia negative symptom, cognitive impairment associated with schizophrenia (CIAS), Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, attention deficit hyperactivity disorder (ADHD), or drug dependency, which comprises administering an effective amount of the compound or a salt thereof according to claim 1 to a subject.