Pigments Formed by the Reaction of o-Acetylbenzophenone with Aniline andα-Branched Primary Amines

Abstract

o-Acetylbenzophenone [1] reacted with aniline in benzene or in methanol in the presence of acetic acid to give a red pigment, C42H30N2 [5 d], mp 257° C, a deep blue pigment, C47F135N3 CH₃CO₂H [ 6 ], mp 275° C and two pale brown compounds, C41H30N2 [l2], mp 185° C and C611143N8 [l3], mp 310° C. However, from [1] and aniline in methanol in the presence of hydrochloric acid, the red pigment C5 dj and the blue pigment, (C41H₂91\12) +0- C3 dp were obtained. This blue pigment [3 d] was also prepared from [l2] and [I3] with hydrochloric acid.
On the basis of their spectra and chemical behaviors, the structures of these products were determined to be acetate of 1-anilino-1-[o- (a-phenyliminobenzyl) phenyl]-2- (2, 3-dipheny1-1- isoindolyl) ethylene C 61 bis-[l2] and tris- (2, 3-diphenyl-1-isoindolyl) methane [l3], respectively. From reaction mixtures of [1] and isopropyl- and cyclohexylamine in the presence of acetic acid, stable deep blue pigments, C_2C91-1, 8NOR 14 e, fD were isolated. By treating these reaction mixtures with hydrochloric acid, (C_2C91-119N2R2) +Cl- 1i3 e, f and [4 e, f] were isolated. However, in the presence of hydrochloric acid [1] did not react with these amines. [3 e, f] changed into [4 e, f] on standing in various solvents.
t-Butylamine did not react with [1] under the same conditions. The mechanisms of the formations of C 6 J and C4 e, fp from [3 e, f] were proposed.