[4 + 2] Cycloadditions of 3-Tetrazolyl-1,2-diaza-1,3-butadienes: Synthesis of 3-Tetrazolyl-1,4,5,6-tetrahydropyridazines.

A large variety of dienophiles, including electron-rich and -deficient 2π components, undergo the title reaction of hydrazones (I) or (XVII) to give the desired pyridazines, and in some cases open-chain hydrazone derivatives.