Compounds of formula (I) or a pharmaceutically acceptable salt, solvate or prodrug thereof, are disclosed: ##STR00001## wherein R.sup.1 is C.sub.1-6alkyl, haloC.sub.1-6alkyl, C.sub.2-6alkenyl, amino, monoC.sub.1-4alkylamino or diC.sub.1-4alkylamino; R.sup.2 and R.sup.3, which may be the same or different, are hydrogen, halogen, C.sub.1-6alkyl, haloC.sub.1-6alkyl, C.sub.1-4alkoxy, haloC.sub.1-4alkoxy, cyano, amino, monoC.sub.1-4alkylamino or diC.sub.1-4alkylamino; each R.sup.4, which may be the same or different, is C.sub.1-6alkyl, halogen, C.sub.1-6alkyl, haloC.sub.1-6alkyl, C.sub.1-4alkoxy, haloC.sub.1-4alkoxy, cyano, nitro, amino, monoC.sub.1-4alkylamino or diC.sub.1-4alkylamino; p is 0, 1 or 2; n is 1 or 2; R.sup.5 and R.sup.6, which may be the same or different, are hydrogen, halogen, C.sub.1-6alkyl, haloC.sub.1-6alkyl, C.sub.1-4alkoxy, haloC.sub.1-4alkoxy, cyano, amino, monoC.sub.1-4alkylamino or diC.sub.1-4alkylamino; and Het is thienyl, pyridyl, pyrimidinyl, pyridazinyl, pyrimidinyl, pyrazinyl, imidazolyl, pyrazolyl, pyrrolyl, quinolyl, thiazolyl or furyl, each of which may be substituted by one or more groups independently selected from the list consisting of C.sub.1-6alkyl, C.sub.1-6alkoxy, acetyl, halogen, haloC.sub.1-6alkyl, cyano, nitro, amino, monoC.sub.1-4alkylamino and diC.sub.1-4alkylamino. Methods of preparation of the compounds, and uses thereof in medicine, for example treatment of schizophrenia, are also disclosed.