Novel 6-aryl benzimidazolones and benzothiazolones were prepared and examined as bioisosteres of the recently reported 6-aryl dihydroquinolines (1) for progesterone receptor (PR) antagonist activities. PR antagonist activities increased when compounds 9c–f possessed a more lipophilic group at position-1 and pendent aryl moiety para to NH moiety. Furthermore, conversion of carbonyl moiety of 9e, f to the thio-carbonyl led to ...