The preparation of some 2-nitroacridines and related compounds

Abstract

The reaction of 2-fluoro-5-trobenzaldehyde with a wide variety of arylamines gives, in general, mixtures of the corresponding 2-arylamino-5-nitrobenzaldehydes and their related anils. Both aldehydes and anils readily underwent acid-catalysed cyclization to give the corresponding 2-nitro-acridines. The effect of substituent on the rate of cyclization of these aldehydes and of some related anilino-benzaldehydes and -acetophenones has been studied in trifluoroacetic acid solution by means of ¹H n.m.r. spectroscopy. A solution of 2-(N-methylanilino)-5-nitrobenzaldehyde in trifluoroacetic acid appears to contain a substituted acridinium ion; treatment of this solution with alkali gave 10-methyl-2-nitroacridone. ¹H n.m.r. data for a wide variety of substituted 2-nitro-acridines are discussed.