Pyrazolopyrimidinones which inhibit type 5 cyclic guanosine 3′,5′—monophosphate phosphodiesterase (cGMP PDE5) for the treatment of sexual dysfunction

A process for the preparation of a compound of formula (IA) or (IB):

• or a pharmaceutically or veterinarily acceptable salt thereof, or a pharmaceutically or veterinarily acceptable solvate of either entity,
• wherein R1 is C1 to C3 alkyl substituted with C3 to C6 cycloalkyl, CONR5R6 or a N-linked heterocyclic group selected from pyrazolyl, imidazolyl, triazolyl, pyrrolidinyl, piperidinyl, morpholinyl and 4-R9-piperazinyl;
• (CH2)nHet or (CH2)nAr;
• R2 is C1 to C6 alkyl;
• R3 is C1 to C6 alkyl optionally substituted with C1-C4 alkoxy;
• R4 is SO2NR7R8;
• R5 and R6 are each independently selected from H and C1 to C4 alkyl optionally substituted with C1 to C4 alkoxy, or, together with the nitrogen atom to which they are attached, form a pyrrolidinyl, piperidinyl, morpholinyl or 4-R9-piperazinyl group;
• R7 and R8, together with the nitrogen atom to which they are attached, form a 4-R10-piperazinyl group;
• R9 is C1 to C4 alkyl;
• R10 is H or C1 to C4 alkyl optionally substituted with OH, C1 to C4 alkoxy or CONH2;
• Het is a C-linked 6-membered heterocyclic group containing one or two nitrogen atoms as the only heteroatoms therein, optionally in the form of its mono-N-oxide, or a C-linked 5-membered heterocyclic group containing from one to four heteroatoms selected from nitrogen, oxygen and sulphur, wherein either of said heterocyclic groups is optionally substituted with one or two substituents selected from C1 to C4 alkyl optionally substituted with C1 to C4 alkoxy, C1 to C4 alkoxy, halo and NH2;
• Ar is phenyl optionally substituted with one or two substituents selected from C1 to C4 alkyl, C1 to C4 alkoxy, halo, CN, CONH2, NO2, NH2, NHSO2 (C1 to C4 alkyl) and SO2NH2;
• and n is 0 or 1;
• which comprises reacting a compound of formula (IIA) or (IIB), respectively:
• wherein Y is halo, and R1, R2 and R3 are as previously defined in this claim, with a compound of formula (III):
• R7R8NH (III)
• wherein R7 and R8 are as previously defined in this claim, optionally followed by formation of a pharmaceutically or veterinarily acceptable salt of the required product or a pharmaceutically or veterinarily acceptable solvate of either entity.