The present invention is directed to compounds of formula (I), and the pharmaceutically acceptable acid addition salts thereof, wherein R is selected from the group consisting of F,--CF.sub.3, --OCH.sub.3, --O(C.sub.1)alkyl substituted with 1 to 3 fluoro atoms. --O(C.sub.2) substituted with 1 to 5 fluoro atoms, and --O(C.sub.3)alkyl substituted with 1 to 7 fluoro atoms. The compounds of formula (I) are useful in the treatment of stroke, traumatic brain injury and central nervous system degenerative diseases.