Hydrochloric Acid → 2,3,4,5-Tetrahydro-5-oxothieno[3,2-f]-1,4-thiazepin-4-acetaldehyde

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Reaction Steps

To a solution of 8.0 g of 2,3-dihydrothieno[3,2-f]-1,4-thiazepin-5(4H)-one in 160 ml of N,N-dimethylformamide was added 6.3 g of potassium t-butoxide with stirring under ice-cooling and the mixture was stirred for an hour at room temperature. Then to the mixture was added 8.4 ml of bromoacetaldehyde diethyl acetal under ice-cooling. The mixture was stirred for 5 hours at room temperature and water was added thereto and extracted with ethyl acetate. The extract was washed with water, dried over magnesium sulfate and the solvent was distilled off. The residue was chromatographed on a silica gel using and chloroform and methanol (98.8:0.2) as an eluent to give 6,9 g of 4-(2,2-diethoxyethyl)-2,3-dihydrothieno[3,2-f]1,4-thiazepin-5(4H)-one as a pale yellow oil. To the solution of thus obtained 6.7 g of 4-(2,2-diethoxyethyl)-2,3-dihydrothieno[3,2-f]-1,4-thiazepin-5(4H)-one in 150 ml of tetrahydrofuran was added 20 ml of 10% hydrochloric acid and the mixture was allowed to stand for 20 hours at room temperature, and then poured into water and extracted with ethyl acetate. The extract was washed with water, dried over magnesium sulfate and the solvent was distilled off to give 4.4 g of 2,3,4,5-tetrahydro-5-oxothieno[3,2-f]-1,4-thiazepin-4-acetaldehyde as a pale yellow oil.

Provenance & Evidence