1-Benzothiophene-2-carbaldehyde → (E)-3-(benzo[b]thienyl)-2-propenoic acid ethyl ester

Participants

Reaction Steps

To a solution of benzo[b]thiophene-2-carboxaldehyde (4.40 g, 27.1 mmol) and triethyl phosphonoacetate (16.6 mL, 83.2 mmol) in absolute EtOH (120 mL) was added a solution of EtONa/EtOH (made from 1.92 g of Na and 70 mL of EtOH) at 40° C. with stirring. The mixture was then heated at reflux for 40 min. After cooling to r.t. the mixture was concentrated to remove most of the solvent, mixed with crushed ice (60 mL) and water (60 mL), and was extracted with Et2O (3×450 mL). The combined extracts were washed with brine (2×200 mL), dried (MgSO4), and evaporated to dryness. The crude solid was purified by a flash chromatography on silica gel using 15% EtOAc/hexane as the eluent to give-(E)-3-(benzo[b]thien-2-yl)-2-propenoic acid ethyl ester (4.44 g, 19.1 mmol) in 71% yield as an amorphous solid.

Provenance & Evidence