Disclosed are the compounds of formula I ##STR00001## wherein R is methyl or ethyl; R.sub.1 is chloro or fluoro; R.sub.2 is hydrogen or fluoro; R.sub.3 is hydrogen, fluoro, chloro, methyl, ethyl, methoxy, ethoxy or hydroxy; R.sub.4 is hydrogen or fluoro; and R.sub.5 is chloro, fluoro, trifluoromethyl or methyl; and pharmaceutically acceptable salts thereof, as selective COX-2 cyclooxygenase inhibitors; and pharmaceutically acceptable prodrug esters thereof.