The reaction of 9-(3,6-diphenylpyridazin-4-yl)-4-azafluorene with n-butyl acrylate under conditions of the Michael reaction affords the product of the condensation at the methine group. When sterically hindered esters of methacrylic, crotonic, and cinnamic acid are utilized, the condensation does not occur, and the main reaction product under these conditions is 9-hydroxy-(3,6-diphenylpyridazin-4-yl)-4-azafluorene. The supposition concerning the existence of its conformers (rotamers) with different orientation of the diphenylpyridazinyl ring in relation to the azafluorene fragment was expressed. © 1994 Plenum Publishing Corporation.