To a stirred suspension of sodium hydride (2.88 g., 120 mmole) in dry dimethylformamide (20 ml), under dry nitrogen and cooled in an ice-bath is added dropwise, a solution of diethyl malonate (19.2 g., 120 mmole) in dimethylformamide (30 ml). The mixture is stirred for one hour in the ice-bath and another hour at room temperature, then is cooled in the ice-bath again and 2-cyclopentyl-6,7-dichloro-2-methyl-5-trifluoromethylsulfonyloxy-1-indanone (12.93 g., 30 mmole) in dimethylformamide (25 ml) is added dropwise over 1-1/2 hours. The mixture is stirred at room temperature overnight and then poured into a mixture of ice-water (750 ml), methylene chloride (200 ml) and 6 N hydrochloric acid (20 ml). The methylene chloride layer is separated and the aqueous layer extracted with methylene chloride (50 ml). The combined extract is washed with water (500 ml), dried (MgSO4) and evaporated under vacuum, finally at 70°/0.05 Torr, to give an oil (18.28 g.). This is purified by chromatography on Merck silica gel (1.04 Kg) using 1,1,1-trichloroethane as the solvent. The product is accompanied by some diethyl malonate which is removed at 125°/0.05 Torr to give a viscous oil, 10.25 g. (77%),
