Compounds of formula (I), salts and solvates thereof are provided: ##STR00001## wherein Ar is selected from phenyl, pyridyl and thienyl optionally substituted with one or more groups Y; and each Y group is independently selected from the group consisting of: halo, C.sub.1-4alkyl, haloC.sub.1-4alkyl, C.sub.1-4alkoxy, cyano, C(O)C.sub.1-4alkyl, NHSO.sub.2C.sub.1-4alkyl, NMeSO.sub.2C.sub.1-4alkyl, NHCOC.sub.1-4alkyl, NMeCOC.sub.1-4alkyl, SOC.sub.1-4alkyl, SO.sub.2C.sub.1-4alkyl and CO.sub.2C.sub.1-4alkyl, or two Y groups together form a cyclic group --O(CH.sub.2)O--. Processes for preparation, and uses thereof in the treatment of a disease or condition mediated by a reduction or imbalance in glutamate receptor function, such as schizophrenia or cognition impairment, are also disclosed.