Compounds of formula I are described herein which are agonists or partial agonists of the 2C subtype of brain serotonin receptors. ##STR00001## or pharmaceutically acceptable salts thereof, wherein each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.x, R.sup.y, and n are as defined herein. Such compounds, and compositions thereof, are useful for treating a variety of central nervous system disorders such as schizophrenia.