Synthesis of Functionalized Pyridazines from 1,2-Diaza-1,3-butadienes

Significance

A synthesis of functionalized pyridazines from 4-chloro-1,2-diaza-1,3-butadiene and active methylene compounds has been ­reported. The reaction may be mechanistically viewed as a Michael-type addition followed by a dehydrohalogenation to give α,β-unsaturated ­hydrazone which subsequently undergoes an intramolecular heterocyclization-decarbamoylation upon treatment with NaOMe to give the pyridazine product. Interestingly, if 4-alkoxy- and 4-dialkyl-amino-1,2-diaza-1,3-butadiene are used as starting materials, pyrrole rather than pyridazine products are observed (O. A. Attanasi et al. ARKIVOC 2002, (xi), 274).