Mechanism of the Fujiwara Reaction: Structural Investigation of Reaction Products from Benzotrichloride.

Article abstract of DOI:10.1021/jo00329a004

The mechanism of color development and the structures of chromophores of the Fujiwara reaction have been investigated by using benzotrichloride as a chromogenic reagent.Two products were isolated.NMR and mass spectroscopic investigation indicates that one of them is N²-<(1E,3E)-1,3-butadienyl>-N¹-(1,3-butadienyl)benzamidine and that the other is N-<(1E,3E)-4-methanoyl-1,3-butadienyl>benzenecarboxamide.In alkaline media, the former develops an intense red color; the latter becomes yellow.The formation of these chromophores is explained by the hydrolytic scission of pyridine rings in the benzal dipyridinium cation intermediate.