4-Chlorobenzaldehyde → 5-[(4-Chlorophenyl)methylidene]-2,2-dimethylcyclopentan-1-one

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Reaction Steps

10% aqueous sodium hydroxide solution (100 ml) is added to a mixture of 2,2-dimethylcyclopentanone (10 g) and 4-chlorobenzaldehyde (13.8 g) in ethanol (100 ml) at 0° C. After 30 minutes, a thick slurry is filtered and the solid is washed and then dried. 2,2-Dimethyl-5-(4-chlorobenzylidene)-1-cyclopentanone (12.5 g), m.p. 120° C., is obtained. This compound, dissolved in THF (50 ml), is added to a solution formed in the following manner: sodium hydride (80% dispersion in mineral oil) (1.9 g) in anhydrous DMSO (50 ml) is heated to 80° C. until the solid has dissolved completely. The solution is then diluted with THF (100 ml) and then cooled to -10° C. A solution of trimethylsulphonium iodide (11.5 g) in dimethyl sulphoxide (80 ml) is added to the mixture in the course of 10 minutes and the mixture is stirred for 15 minutes at -10° C. A solution of 2,2-dimethyl-4-chloro-5-(4-chlorobenzylidene)-1-cyclopentanone (11.8 g) in THF (100 ml) is then added.

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