Hydrochloric Acid → 3-Methyl-4-hydroxy-7-(2-thienoyl)benzofuran

Participants

Reaction Steps

A solution of freshly prepared pyridinium hydrochloride (4.84 g, 41.9 mmol) and 3-methyl-4-methoxy-7-(2-thienoyl)benzofuran (2.30 g, 8.38 mmol) in quinoline (10 mL) was heated to reflux for 2.5 hours. The mixture was cooled, an additional portion of pyridinium hydrochloride added (2.42 g, 20.9 mmol) and reflux was resumed for one hour. After cooling the reaction mixture was poured into water (200 mL) and acidified with 2N HCl. The resulting mixture was extracted with chloroform (5×50 mL) and the combined organic extracts were washed with water (50 mL), dried (Na2SO4), and concentrated. Chromatographic purification by preparative HPLC using 25% ethyl acetate in hexane as eluant afforded 3-methyl-4-hydroxy-7-(2-thienoyl)benzofuran compound 3 along with recovered starting material. A sample of the desired product was recrystallized from ether/hexane. 1H NMR d 2.45 (3H, s), 6.24 (1H, br s), 6.45 (1H, d, J=8 Hz), 7.17 (1H, dd, J=4 Hz, 4 Hz), 7.37 (1H, s), 7.61 (1H, d, J=8 Hz), 7.67 (1H, d, J=4 Hz), 7.75 (1H, d, J=4 Hz).

Provenance & Evidence