Acridine Synthesis by the Reaction of 2-(Perfluoroalkyl)aniline with ortho-Alkyl-Substituted Aromatic Grignard Reagent: Mechanistic Studies

The reaction of 2-(perfluoroethyl)aniline and its higher perfluoroalkyl analogues with an arylmagnesium bromide substituted with a methyl or ethyl group at the ortho position furnishes an acridine containing a shorter perfluoroalkyl group at the 9-position and devoid of the methyl or ethyl group of the Grignard reagent. Yields are in the range of 46–93 %. The intermediary of a substituted aza-ortho-xylylene has been postulated for related transformations in the literature previously, but this intermediate product has never been isolated. As part of this work, the labile product E-27 (half-life of 6 h at 23°C) was isolated for the first time and characterized by infrared spectroscopy, electron impact mass spectrometry, fast atom bombardment mass spectrometry, and 1H NMR. Experimental evidence was also obtained regarding the elimination of the ortho-alkyl group of the Grignard reagent during the course of the reaction as an alcohol.