Abstract: The present invention relates to novel compounds of formula (I) or a pharmaceutically acceptable salt thereof: wherein R1 is hydrogen or C1-4alkyl; R2 is C1-4alkyl; R3 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 and SF5; p is 0, 1, 2, 3 or 4; and R4 is independently selected from a group consisting of: halogen, hydroxy, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy, haloC1-4alkoxy and C1-4alkanoyl; n is 0 or 1; wherein when R4 is chlorine and p is 1, such R4 is not present in the ortho position with respect to the linking bond to the rest of the molecule; and wherein, if n is 0, R3 comprises at least one SF5 group as a substituent; processes for their preparation, intermediates used in these processes, pharmaceutical compositions conta