Ethyl Acetate → 2-(3,3-diethoxypropyl)-3,4-dihydro-2-(3,4-dimethoxyphenyl)-4-methyl-3-oxo-2H-1,4-benzothiazine

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Reaction Steps

To a stirred suspension of 60% sodium hydride (0.6 g) in dimethylformamide (5 ml), 3,4-dihydro-2-(3,4-dimethoxyphenyl)-4-methyl-3-oxo-2H-1,4-benzothiazine (4.4 g) dissolved in dimethylformamide (15 ml) is added under nitrogen atmosphere and ice-cooling, and the mixture is stirred for 15 minutes at room temperature. β-Chloropropionaldehyde diethyl acetal (2.8 g) is added to the reaction mixture, and the mixture is stirred for 2.5 hours at 60° C. The mixture is poured into a mixture of ethyl acetate and water. The organic layer is washed with 1N sodium hydroxide and saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate and concentrated in vacuo. The residue is purified by silica gel column chromatography to give 4.4 g (71.5 %) of 2-(3,3-diethoxypropyl)-3,4-dihydro-2-(3,4-dimethoxyphenyl)-4-methyl-3-oxo-2H-1,4-benzothiazine as an oily form (compound No. 36, (IR: neat, cm-1) 1660, 1588, 1444, 1325, 1238, 750).

Provenance & Evidence