[Unexpected anti-inflammatory activity of rigid structure derivatives of 6-arylpyridazinone antihypertensives. I. Synthesis and activity of 4,4a-dihydro-5H-indeno[1,2c]pyridazin-3-ones].

The antihypertensive 5-methyl-6-p.cyanophenyl-4,5-dihydro-3(2H)-pyridazinone has been embodied in a rigid framework corresponding to a 4,4a-dihydro-5H-indeno[1,2-c]-3-pyridazinonic structure (II). The resulting 7-cyano derivative (IIc) was found to be devoid of antihypertensive activity. However this compound, as well as other members having structure (II), exhibited antiinflammatory properties.