Disclosed are compounds of the formula ##STR00001## and the pharmaceutically acceptable salts thereof wherein R, Ar, A, n, R.sub.1 and R.sub.2 are defined herein. These compounds are highly selective agonists, antagonists or inverse agonists for GABA.sub.A brain receptors or prodrugs of agonists, antagonists or inverse agonists for GABA.sub.A brain receptors and are therefore useful in the diagnosis and treatment of anxiety, depression, Down Syndrome, sleep and seizure disorders, overdose with benzodiazepine drugs and for enhancement of memory. Pharmaceutical compositions, including packaged pharmaceutical compositions, are also disclosed.