A non-obvious reaction pathway in the formation of 2-aminobenzene-1,3-dicarbonitriles from α,β-unsaturated ketones or aldehydes

Abstract

Key intermediates demonstrating a non-obvious reaction pathway leading to 2-aminobenzene-1,3-dicarbonitriles from enones have been isolated and characterised in the reaction between ( E)-4-phenyl-3-butene-2-one and propanedinitrile in a basic hydro-alcoholic medium. ( E)-4-Phenyl-3-butene-2-one reacts with three molecules of propanedinitrile to give a 6-amino-2-iminobicyclo[2.2.2]-5-octene-1,3,3,5-tetracarbonitrile system which evolves to a substituted cyclohexadiene by elimination of the sodium salt of 1,1,1-tricyanomethane. Further oxidation leads to the final 2-aminobenzene-1,3-dicarbonitrile. The proposed pathway involves more steps and more difficult transformations than previously presented for similar systems. We can not exclude a simpler reaction pathway derived from the double Michael and Knoevenagel adduct of ( E)-4-phenyl-3-butene-2-one and propanedinitrile, however we have not found any evidence for this simpler process.