The present invention provides a composition comprising a compound of
formula I: or a pharmaceutically acceptable salt thereof, wherein each
of R.sup.1, R.sup.2, R.sup.3, y, n, and Ar are as defined, and described
in classes and subclasses herein, which are agonists or partial agonists
of the 2C subtype of brain serotonin receptors. Such compounds, and
compositions thereof, are useful for treating a variety of central
nervous system disorders such as schizophrenia.