2-(piperidin-4-yl)-4,5-dihydro-2H-pyridazin-3-one derivatives as PDE4 inhibitors

1. A compound of formula I

in which

R1 is methyl or ethyl,

R2 is methyl or ethyl,

R3 represents a phenyl derivative of formula (b)

wherein

R6 is methoxy, ethoxy or difluoromethoxy,

R7 is methyl and

R8 is hydrogen,

or wherein

R7 and R8 together and with inclusion of the two carbon atoms, to which they are bonded, form a spiro-linked cyclopentane, cyclohexane, tetrahydrofuran or tetrahydropyran ring,

R9 is —(CH 2 ) n —C(O)—R18,

R18 is —N(R19)R20,

R19 is hydrogen or 1-4C-alkyl,

R20 is hydrogen or 1-4C-alkyl,

or R19 and R20 together and with inclusion of the nitrogen atom to which they are bonded, form a 1-pyrrolidinyl-, 1-piperidinyl-, 1-piperazinyl, 1-(1-4C-alkyl)-piperazin-4-yl-, 1-hexahydroazepinyl-, 4-morpholinyl or 4-thiomorpholinyl-ring,

n is 1 or 2,

or a salt thereof.

2. A compound of formula 1

in which

R1 is methyl or ethyl,

R2 is methyl or ethyl,

R3 represents a phenyl derivative of formula (b)

wherein

R6 is methoxy, ethoxy or difluoromethoxy,

R7 is methyl and

R8 is hydrogen,

or wherein

R7 and R8 together and with inclusion of the two carbon atoms, to which they are bonded, form a spiro-linked cyclopentane, cyclohexane, tetrahydrofuran or tetrahydropyran ring,

R9 is —C(O)—(CH 2 ) m —R21,

R21 is —N(R22)R23,

R22 is hydrogen or 1-4C-alkyl,

R23 is hydrogen or 1-4C-alkyl,

or R22 and R23 together and with inclusion of the nitrogen atom to which they are bonded, form a 1-pyrrolidinyl-, 1-piperidinyl-, 1-piperazinyl, 1-methyl-piperazin-4-yl-, 1-hexahydroazepinyl-, 4-morpholinyl, 4-thiomorpholinyl-, pyrrolidin-2,5-dione-1-yl-, morpholin-3,5-dione-4-yl-, piperidin-2,6-dione-1-yl, 4,4-dimethyl-piperidin-2,6-dione-1-yl or a 1-methyl-imidazolidine-2,4-dione-3-yl-ring or a isoindol-1,3-dione-2-yl-ring-system,

m is 1,

or a salt thereof.

3. A compound of formula I according to claim 2 , in which

R1 is methyl or ethyl,

R2 is methyl or ethyl,

R3 represents a phenyl derivative of formula (b)

wherein

R6 is methoxy,

R7 is methyl and

R8 is hydrogen,

R9 is —C(O)—(CH 2 ) m —R21,

R21 is —N(R22)R23,

or R22 and R23 together and with inclusion of the nitrogen atom to which they are bonded, form a 1-methyl-piperazin-4-yl-, pyrrolidin-2,5-dione-1-yl- or a morpholin-3,5-dione-4-yl-ring or a isoindol-1,3-dione-2-yl-ring-system,

m is 1,

or a salt thereof.

4. A pharmaceutical composition comprising one or more compounds according to claim 1 , or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable auxiliary and/or carrier.

5. A pharmaceutical composition comprising one or more compounds according to claim 2 , or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable auxiliary and/or carrier.

6. 2-{4-[3-(7-Methoxy-2,2-dimethyl-2,3-dihydro-benzofuran-4-yl)-5,5-dimethyl-6-oxo-5,6-dihydro-4H-pyridazin-1-yl]-piperidinyl-1-yl}-acetamide or a salt thereof.

7. 6-(7-Methoxy-2,2-dimethyl-2,3-dihydro-benzofuran-4-yl)-4,4-dimethyl-2-{1-[2-(4-methyl-piperazin-1-yl)-ethanoyl]-piperidin-4-yl}-4,5-dihydro-2H-pyridazin-3-one.

8. 1-(2-{4-[3-(7-Methoxy-2,2-dimethyl-2,3-dihydro-benzofuran-4-yl)-5,5-dimethyl-6-oxo-5,6-dihydro-4H-pyridazin-1-yl]-piperidin-1-yl}-2-oxo-ethyl)-pyrrolidine-2,5-dione.

9. A pharmaceutical composition comprising the compound according to claim 6 , or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable auxiliary and/or carrier.

10. A pharmaceutical composition comprising the compound according to claim 7 , together with a pharmaceutically acceptable auxiliary and/or carrier.

11. A pharmaceutical composition comprising the compound according to claim 8 , or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable auxiliary and/or carrier.