Novel arylpiperazine derivatives

Compounds of the formula (I):

• in which:
• R1 represents a heteroaryl with five or six chain links, containing one or more heteroatoms, selected from among 2-pyridyl, 2-pyrimidinyl, 2-pyridazinyl, 2-pyrazinyl, 2-imidazolyl, 2-oxazolyl, 2-thiazolyl, 3-isoxazolyl, 3-isothiazolyl, 1,2,4-triazol-2-yl, 1,3,4-oxadiazol-2-yl, 1,3,4-thiadiazol-2-yl, optionally substituted, in addition to its two attachments, by one or more identical or different groups selected from among a halogen atom or a hydroxy, alkyl, monofluoroalkyl, polyfluoroalkyl, alkoxy, polyfluoroalkoxy, alkylsulfanyl, polyfluoroalkylsulfanyl group;
• Ar is an aryl or heteroaryl fused with R1 and optionally substituted by one or more identical or different substituents selected from among a halogen atom or alkyl, monofluoroalkyl, polyfluoroalkyl, alkoxy, polyfluoroalkoxy, alkylsulfanyl, polyfluoroalkylsulfanyl, cyano, carbamoyl, dialkylcarbamoyl, alkyl-C(═O)—, alkyl-O—C(═O)—, HO—C(═O)—, (HO)alkyl group;
• a=2, 3 or 4;
• b and c, identical or different, represent 1 or 2;
• R2, R3, R4, R5 and R6 each independently represent a hydrogen or halogen atom or a hydroxy, alkyl, monofluoroalkyl, polyfluoroalkyl, alkoxy, polyfluoroalkoxy, alkylsulfanyl, polyfluoroalkylsulfanyl, cyano, —NRR′, —COOR, —COR, —CONRR′ group or alternatively two adjacent R2, R3, R4, R5 and R6 are joined to one another to form a hydrocarbon cycle or a saturated or unsaturated heterocycle, fused to the phenyl nucleus to which they are attached;
• where R, R′, identical or different, independently represent a hydrogen atom, or an alkyl group;
• together with stereoisomers or mixtures thereof, the tautomeric forms thereof, the pharmaceutically acceptable salts thereof,
• with the exception of those compounds for which:
• R1 represents a 2-oxazolyl, 2-imidazolyl or 2-thiazolyl fused to the Ar group=optionally substituted phenyl,
• and compounds for which:
• R1 represents a 2-pyridyl group, fused to the Ar group=phenyl optionally substituted by Me in position 4 of the resultant quinoline cycle, a=2, b=c=1, R2=H, OMe and R3—R6=H or R2=R3=Me and R4—R6=H;
• R1 represents a 2-pyrimidinyl group, fused to the Ar group=phenyl substituted by OMe in positions 6 and 7 and —OH in position 4 or 6 of the resultant quinazolinyl cycle, a=2, b=c=1, R2=R3=R4=R5=H and R6=OMe.