Hydrochloric Acid → Dimethyl 2,5-bis{(4-fluorophenyl)amino}cyclohexa-1,4-diene-1,4-dicarboxylate

Dimethyl 1,4-cyclohexanedione-2,5-dicarboxylate (9.12 gm; 40 mmol) and methanol (200 ml) were heated to boiling, then 4-fluoroaniline (8.35 ml (9.78 gm); 42 mmol) was added followed by conc. hydrochloric acid (400 μl). The mixture was refluxed for 3 hours under a nitrogen atmosphere. On cooling a yellow solid precipitated out which was collected by filtration, washed with methanol and dried under vacuum to give 15.8 gm (96%) of dimethyl 2,5-bis{(4-fluorophenyl)amino}cyclohexa-1,4-diene-1,4-dicarboxylate.