Unusual [4+2]-Cycloaddition Reaction between Electron-Poor 1,2-Diaza-1,3-dienes and Electron-Poor Alkenes: Useful Entry to Novel Tetrahydropyridazines - D’Auria, Maurizio; Racioppi, Rocco; Attanasi, Orazio A.; Mantellini, Fabio (Synlett, 2010)