Hydrochloric Acid → 2-(3-Formyl-benzyl)-1,1-dioxo-1lambda6 isothiazolidine-3-carboxylic acid methyl ester

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Reaction Steps

3-Bromomethyl-benzaldehyde (2.44 g, 12.3 mmol) and cesium carbonate (9.08 g, 27.9 mmol) were added to a solution of a 4:3 mixture of 1,1-dioxo-isothiazolidine-3-carboxylic acid methyl ester and 1,1-dioxo-isothiazolidine-3-carboxylic acid ethyl ester (Intermediate 7 Step 2; 2.01 g, 10.8 mmol) in N,N-dimethylformamide (60 mL). The mixture was stirred at room temperature for 20 h and then dichloromethane (100 mL) was added. Saturated aqueous ammonium chloride solution (25 mL) was added followed by 1 M hydrochloric acid to bring the pH to 2-3. The two layers were separated and the organic layer was washed twice with brine. The solution was dried over sodium sulfate, and filtered. Celite was added and the solvents were evaporated under reduced pressure. The residue (containing the mixture of crude products coated onto Celite) was purified using flash chromatography (Analogix SF40-240 g Si), eluting with 30-70% ethyl acetate/hexanes to give 2-(3-formyl-benzyl)-1,1-dioxo-1λ6 isothiazolidine-3-carboxylic acid ethyl ester (first eluting peak; 1.26 g, 37%) and 2-(3-formyl-benzyl)-1,1-dioxo-1λ6 isothiazolidine-3-carboxylic acid methyl ester (second eluting peak; 1.69 g, 53%).

Provenance & Evidence