Investigation of hydrazine addition to functionalized furans: synthesis of new functionalized 4,4′-bipyrazole derivatives

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.