Cl CO2H NH2 Cl HO2C Cl CO2H 1 i,ii O O O Cl Cl O Cl Cl iii iv 2 3 72% 73% O Cl Cl O R2N NR2 3 4 5 NH2 O Me2N NMe2 i,ii iii,iv 35-71% 65% J. CHEM. RESEARCH (S), 1997 183 J. Chem. Research (S), 1997, 183 J. Chem. Research (M), 1997, 1252–1261 A Convenient Route to 3,6-Diaminofluoren-9-ones Stephane G. R. Guinot, John D. Hepworth* and Mark Wainwright Department of Chemistry, University of Central Lancashire, Preston PR1 2HE, UK The synthesis of fluoren-9-ones having a 3,6-bis(tertiary amino) functionality is described, in which the amino groups are introduced using either cyclic secondary amines or their N-formylated derivatives to effect nucleophilic displacement of the halogen from 3,6-dichlorofluoren-9-one, which is derived from 4-chloroanthranilic acid.As part of our studies of di- and tri-arylmethane dyes, we have reported the synthesis of some 4,4p-diaminobenzophenones, 16 analogues of Michler’s ketone, the 4,4p-bis(dimethylamino) derivative. We now describe the preparation of some cyclic analogues, 3,6-diaminofluoren-9-ones, from the commercially available 4-chloroanthranilic acid.On treatment with a cuprammonium reagent, diazotised 4-chloroanthranilic acid underwent a self-coupling process which yielded 5,5p-dichlorobiphenyl-2,2p-dicarboxylic acid (1). Conversion into the anhydride 2, achieved by boiling with acetic anhydride, was followed by in situ pyrolysis at ca. 400 °C to give 3,6-dichlorofluoren-9-one (3) in 53% overall yield (Scheme 1).The nucleophilic displacement of halides in an aromatic environment is known to be promoted by the presence of electron-withdrawing functionalities. However, unless such activation is particularly efficient, as for example in Sanger’s reagent where the preferred halogen,15 fluorine, is activated by two nitro groups, quite severe conditions are necessary. Cyclic secondary amines provide not only a good nucleophilic centre but also enable high reaction temperatures to be achieved and react with 4,4p-difluorobenzophenone to give the corresponding diamino ketone.16 Although not a powerfully activated halogen, both chlorine atoms were displaced from 3,6-dichlorofluoren-9-one by a variety of amine nucleophiles in boiling sulfolane.The aminofluorenones 4b–d were also obtained when the aminating species was derived from the corresponding N-formylamines under basic conditions19 (Scheme 2). Although halide displacement from activated chloro compounds by boiling with N,N-dimethylformamide is well documented, 20 3,6-bis(dimethylamino)fluoren-9-one (4a) could not be obtained in this manner.Similar failure attended the use of N,N-diethylformamide. 3,6-Bis(dimethylamino)fluoren-9-one (4a) was obtained in good yield from 2-amino-4,4p-bis(dimethylamino)benzophenone (5) via diazotisation and intramolecular coupling of the derived radicals under acidic conditions. Careful control of the conditions are essential to the success of the reaction.Techniques used: 1H NMR, flash chromatography References: 25 Schemes: 2 Received, 24th January 1997; Accepted, 27th February 1997 Paper E/7/00560A References cited in this synopsis 15 N. B. Chapman and R. E. Parker, J. Chem. Soc., 1951, 3301; H. Bader, A. R. Hansen and F. J. McCarty, J. Org. Chem., 1966, 31, 2319. 16 S. F. Beach, J. D. Hepworth, P. Jones, D. Mason, J. Sawyer, G. Hallas and M. M. Mitchell, J. Chem. Soc., Perkin Trans. 2, 1989, 1087. 19 T. Watanabe, Y. Tanaka, K. Sekida, Y. Akita and A. Ohta, Synthesis, 1980, 39. 20 N. D. Heindel and P. D. Kennewell, J. Chem. Soc., Chem. Commun., 1969, 38. *To receive any correspondence. Scheme 1 Reagents and conditions: i, HCl, NaNO2 (aq.), 0 °C; ii, CuSO4 (aq.), NH3 (aq.), NH2OH.HCl (aq.), NaOH (aq.); iii, Ac2O, heat; iv, 400 °C Scheme 2 Reagents and conditions: i, R2NH, sulfolane, heat; ii, R2NCHO, KOH, heat; iii, H2SO4, NaNO2, dil. H2SO4, 0–5 °C; iv, Cu bronze, Na2SO4, 90 °C