this invention encompasses compounds of the formula : ## str1 ## and pharmaceutically acceptable non - toxic salts thereof wherein : n is 0 , 1 , or 2 , x is ## str2 ## and r 1 , r 2 , r 3 , w and y are variables these compounds are highly selective agonists , antagonists or inverse agonists for gabaa brain receptors or prodrugs thereof and are useful in the diagnosis and treatment of anxiety , sleep , and seizure disorders , overdose with benzodiazepine type drugs , and enhancement of alertness .