“…In the accompanying paper [5], we have described the preparation of 3-amino-4,5,6-triphenyl pyridazine a useful starting material for the preparation of 7,8,9-triphenyl-2H-pyrimido [1,2-b]pyridazine-2,4(3H)-dione, 1. In this paper, we wish to show that compound 1 is also useful building blocks for the synthesis of a wide variety of pyrimidopyridazine derivatives and to test their anti-microbial activity.…”