A Straightforward Approach toward Multifunctionalized Pyridazines via Imination/Electrocyclization

A facile synthesis
of functionalized 3-carbamide pyridazines starting
from readily available chlorovinyl aldehydes and oxamic acid thiohydrazides
via cascade imination/electrocyclization is reported. In the presence
of p-toluenesulfuric acid, various ketones have been
efficiently incorporated into the pyridazine derivatives through a
two-step sequence involving a Vilsmeier–Haack reaction and
imination. The synthetic value of this method has been demonstrated
by efficient synthesis of steroidal pyridazines.