Compounds of formula 2 or pharmaceutically acceptable salts thereof are provided: 1 wherein each of R.sup.1a, R.sup.2a, R.sup.3a, Ar, y, and m are as defined herein, which are agonists or partial agonists of the 2C subtype of brain serotonin receptors. The compounds, and compositions containing the compounds, are used to treat a variety of central nervous system disorders such as schizophrenia.