The present invention relates to novel compounds of formula (I) or a pharmaceutically acceptable salt thereof: 1. wherein G is selected from a group consisting of: phenyl, pyridyl, benzothiazolyl, indazolyl; p is an integer ranging from 0 to 5; R1 is independently selected from a group consisting of: halogen, hydroxy, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy, haloC1-4alkoxy, C1-4alkanoyl; or corresponds to a group R5; R2 is hydrogen or C1-4alkyl; R3 is C1-4alkyl; R4 is hydrogen, or a phenyl group, a heterocyclyl group, a 5- or 6-membered heteroaromatic group, or a 8- to 11-membered bicyclic group, any of which groups is optionally substituted by 1, 2, 3 or 4 substituents selected from the group consisting of: halogen, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy, C1-4alkanoyl; R5 is a moiety selected from the group consisting of: isoxazolyl, —CH2—N -pyrrolyl, 1,1-dioxido-2-isothiazolidinyl, thienyl, thiazolyl, pyridyl, 2 -pyrrolidinonyl, and such a group is optionally substituted by one or two substituents selected from: halogen, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy, C1-4alkanoyl; and when R1 is chlorine and p is 1, such R1 is not present in the ortho position with respect to the linking bond to the rest of the molecule; and when R1 corresponds to R5, p is 1; or a salt thereof which are useful as modulators of dopamine D3 receptors, e.g. to treat drug dependency or as antipsychotic agents.