The addition of hydrazine to functionalized furans 2a–d leads to a variety of 4, 4′- bipyrazoles 4a–c depending on the structure of the starting materials. In one example, compound 2c was first converted to an intermediate, furo [3, 4-d] pyridazine 3c which was then transformed into 4, 4′-bipyrazole 4c on reacting with hydrazine.
