A mixture of 2-chloro-1,4-naphthoquinone (3.95 g, 0.02 mol), 4-(4-chlorophenyl)cyclohexane-1-carboxylic acid (4.9 g, 0.02 mol) and powdered silver nitrate (1.05 g, 0.0062 mol) was heated to reflux with vigorous stirring in 40 ml of acetonitrile. A solution of ammonium persulphate (12.0 g, 0.0525 mol) in 50 ml of water was added dropwise over 1 hour. The mixture was refluxed for 3 hours then cooled in ice for 30 mins, after which it was filtered, and the residual sticky solid extracted twice with boiling chloroform to remove inorganic material. The chloroform was removed by evaporation to leave a yellow-brown solid (ca 2.7 g). This was dissolved in 40 ml of boiling acetonitrile; a little insoluble material was removed by filtration. On cooling, the title compound separated as yellow crystals, (550 mg) m.p. 172°-175° C.
