Hydrochloric Acid → 4-Bromo-5-(chloroacetyl)thiophene-2-carbonitrile

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Reaction Steps

Butyllithium (2.5 M solution in hexanes; 14.5 mL, 36.3 mmol) was added under nitrogen over approximately 5 min to a solution of 4-bromo-thiophene-2-carbonitrile (5.95 g, 31.6 mmol) in 300 mL of anhydrous tetrahydrofuran at dry ice-acetone temperature. After the addition, the reaction was stirred at dry ice-acetone temperature for 30 min. 2-Chloro-N-methoxy-N-methyl acetamide (4.80 g, 32.7 mmol) in 40 mL of anhydrous tetrahydrofuran was then added dropwise over 30 min. After the addition, the reaction was stirred at dry ice-acetone temperature for 4 h. 6 M HCl (36 mL) was added and the reaction allowed to warm to room temperature. The reaction was concentrated under reduced pressure to remove the tetrahydrofuran. The residue was partitioned between ethyl acetate and water. Saturated sodium chloride was added to aid in the separation of an emulsion. The organic layer was separated, washed with water, saturated sodium chloride, dried (MgSO4), filtered and the solvent removed under reduced pressure. The residue was purified on 800 g of silica gel (230-400 mesh) using a gradient of 30% methylene chloride in hexane to 60% methylene chloride in hexane as the eluent. Isolation of the major component gave 4-bromo-5-(chloroacetyl)thiophene-2-carbonitrile (1.81 g, 22%) as a white solid, mp 126-128° C.; MS (ESI) m/z 262.

Provenance & Evidence