. "When R4 is substituted phenyl it is preferably substituted at the 4-position with fluoro and/or substituted at the 3-position with fluoro, chloro, C1-4 alkoxy, methanesulfonamido or acetamido, or R4 is a phenyl di-substituted at the 3,4-position independently with chloro or fluoro, more preferably chloro." . . . .