Condensations of 1,4-Cyclohexanediones and Secondary Aromatic Amines. The Formation of Alkyldiarylamines and Triarylamines

Article abstract of DOI:10.1246/bcsj.57.1586

Condensation of 1,4-cyclohexanedione with N-alkylarylamines gives N-alkyl-N-arylanilines, and that with diarylamines gives triarylamines.A mechanism involving dehydration of monoenamines of the 1,4-dione is proposed for the reaction.Relative rates of substituted N-ethylanilines on competitive reactions plotted vs.Hammet's ? values gave -2.0 as the ρ value.In separate reactions, however, a different tendency is noted for the yield, that is, the ease of reactions with p-chloro and p-nitro derivatives.This discrepancy is explained in terms of acidities of the conjugate acids of the amines used as the actual catalysts.