Reaction of Aminopropanedinitrile 4-Methylbenzenesulfonate with Aromatic Aldehydes

Article abstract of DOI:10.1021/jo00002a031

Aminpropanedinitril 4-methylbenzenesulfonate (ammoniopropanedinitrile p-toluenesulfonate, aminomalonitrile p-toluenesulfonate (tosylate), 1) reacts with aromatic aldehydes in methanolic sodium ethanoate to give diastereoselctively (E,E)-4-amino-1-aryl-3-cyano-4-methoxy-2-aza-1,3-butadienes (3) and trans-3,6-diaryl-2,2,5,5-tetracyanopiperazines (4).The product distribution (3:4) depends on the ratio of reactants and the structures of the substrates.Electron-releasing groups on the 4-position of the phenyl ring favor piperazine (4) formation (method B).The formation of piperazine (4) may involve synthetically useful N-protonated aryl- and cyano-stabilized azomethine ylide tautomerism of prior formed 1-aryl-3,3-dicyano-2-aza-1-propenes. 1,3-Dipolar cycloaddition <4+2> reactions of the highly reactive azomethine ylides with dimethyl 1,2-ethynedicarboxylate (DMAD) give 3,4-dicarbomethoxy-2-cyano-5-aryl-3-pyrrolines, which undergo facile dehydrocyanation to 3,4-dicarbomethoxy-2-cyano-5-arylpyrroles.The possible intermediacy of ketenimines and of aryl- and cyano-stabilized 2-azaallyl anionic intermediates in equilibrium with azomethine ylides is also considered.