Abstract: This invention provides a compound of the formula: ##STR1## and its pharmaceutically acceptable salts, wherein R.sup.1 is halo, C.sub.1 -C.sub.6 alkyl, halo C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy or halo C.sub.1 -C.sub.6 alkoxy; R.sup.2 is hydrogen, C.sub.1 -C.sub.6 alkyl, halo C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkyl-S-, C.sub.1 -C.sub.6 alkyl-SO--, C.sub.1 -C.sub.6 alkyl-SO.sub.2 --, cyclopropyl, phenyl, --NH.sub.2, --NH(CH.sub.3), --NHC(.dbd.O)CH.sub.3, --N(CH.sub.3).sub.2, --N(C.sub.2 H.sub.5).sub.2 or --CH.sub.2 C(.dbd.O)CF.sub.3 ; Ar.sup.1 and Ar.sup.2 are independently phenyl, halophenyl or thienyl; X is NH, O or S; and Y is hydrogen, --COOR.sup.3 or --CONR.sup.4 R.sup.5, wherein R.sup.3, R.sup.4 and R.sup.5 are independently hydrogen or C.sub.1 -C.sub.6 alkyl.