Dimethylformamide → 2-BROMO-6-CHLOROTHIENO[2,3-B]PYRIDINE

Participants

Reaction Steps

1 mole of 2-acetamido-5-bromothiophen was reacted with 1 mole dimethylformamide and 3 moles phosphorus oxychloride under reflux in tetrachloroethane for 3 hours at a temperature of 138° C. The compound of formula V in which R1 represents bromo, X represents chloro, and R2, R3 and R4 represent hydrogen was isolated in a yield of 66%. The remainder of the product was accounted for, mainly as unreacted starting material together with a small amount (ca 1%) of polymeric materials. The specified compound of formula V (2-bromo-6-chloro-thieno{2,3-b}-pyridine) was isolated from the crude product by chromatography on a short column of alumina using light petroleum spirit as eluant. The compound was recrystallised from ethanol and had a melting point of 116° C.

Provenance & Evidence