Substituted 3-anilinoindoles and anilinoacetanilides from the reaction of glyoxal with N-alkylanilines: crystal structure of 5-chloro-3-(4-chloro-N-methylanilino)-1-methylindole

Abstract

Glyoxal monohydrate reacts with N-alkylanilines to give substituted 3-anilinoindoles and anilinoacetanilides in a ratio which, in the absence of catalysts, depends on the amount of water present. Acid catalysts favour formation of indoles. The reaction mechanism is discussed. A single crystal X-ray diffraction study of 5-chloro-3-(4-chloro-N-methylanilino)-1-methylindole (XVIII) is reported: the crystals are monoclinic, with unit-cell dimensions of a= 13.96, b= 13.34, c= 8.96 Å, and β= 114° 33′; space-group P2₁/c.