Hydrochloric Acid → Isopropyl hydrogen 1,3-dithiol-2-ylidenemalonate

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Reaction Steps

A 14.4 g portion of diisopropyl 1,3-dithiol-2-ylidenemalonate (0.05 mol) was dissolved in 50 ml of isopropanol, 2.95 g of potassium hydroxide (0.05 mol) was added to the solution at 30° C., and the resulting mixture was stirred for 1 hour. The solution was acidified with 6N hydrochloric acid and extracted with 200 ml of methylene chloride and washed with water and saturated brine in that order. After drying on magnesium sulfate, the solvent was removed by distillation under a reduced pressure and the resulting residue was crystallized from ether to obtain 8.5 g of isopropyl hydrogen 1,3-dithiol-2-ylidenemalonate in the form of white crystals (yield, 75%). Then, 2.7 g (0.011 mol) of the obtained crystals and 3.6 g (0.012 mol) of 2-chloro-1methylpyridinium p-toluene sulfonate were dissolved in 20 ml of dichloromethane to which was then added dropwise a dichloromethane solution of 0.51 g (0.011 mol) of ethanol and 3.46 g (0.034 mol) of triethylamine at 10° C., subsequently stirring the resulting mixture for 2 hours at room temperature. The reaction solution was poured into ice water, extracted with dichloromethane and then washed with 2N hydrochloric acid, 10% sodium carbonate aqueous solution and water in that order. After drying on magnesium sulfate, the solvent was removed by distillation under a reduced pressure, and the resulting residue was purified by a silica gel column chromatography (n-hexane:ethyl acetate=2:1) to obtain 1.0 g of the title compound in the form of crystals having a melting point of 54° C. (yield, 35%).

Provenance & Evidence