Three-Component Triple Organocascade Synthesis of Hexahydropyridazine Derivatives via a Sequential Michael/Amination/Cyclization Reaction

The organocatalytic asymmetric synthesis of hexahydropyridazines were performed through a unique Michael/amination/cyclization reaction. The organocascade reaction proceeded smoothly between 2-arylidene-1,3-indandiones and aldehydes followed by the addition of azodicarboxylates catalyzed by the privileged organocatalyst α,-α-L-diphenylprolinol trimethylsilyl ether (10 mol%) in the presence of a base additive Et₃N (20 mo%) at 0 C. A series of substituted hexahydropyridazines were obtained in good to high chemical yields (55-78 %) and reasonable to high levels of stereoselectivities (51-93 % ee and 4 : 1 d.r.).