A solution of 4-chloro-2-nitrobenzoyl chloride (1 g) in dry dichloromethane (5 ml) was added at 0°-10° C. to a stirred solution of triethylamine (0.62 ml) and 5-(2-ethylthiopropyl)-6-carbethoxycyclohexane-1,3-dione (1.3 g) in dry dichloromethane (20 ml) and the mixture stirred at ambient temperature for 2 hours. Triethylamine (1.9 g) and acetone cyanohydrin (0.1 ml) were added successively to the solution and the mixture stirred at ambient temperature for a further 18 hours. The mixture was washed successively with 2N hydrochloric acid (10 ml) and water (2×10 ml) dried over magnesium sulphate and evaporated under reduced pressure to give 2-(4-chloro-2-nitrobenzoyl)-5-(2-ethylthiopropyl)-6-carbethoxycyclohexane-1,3-dione (0.6 g), mp 102°-104° C., as an orange crystalline solid.
