Hydrochloric Acid → Methyl 5-(4-fluorobenzoyl)-thieno[2,3-b]thiophene-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

Anhydrous aluminium chloride (136 g) is added in small portions, over a period of 30 minutes, to a mixture of methyl thieno[2,3-b]thiophene-2-carboxylate (40.3 g) and 4-fluorobenzoyl chloride (32.3 g) in methylene chloride (1000 cc) at about 25° C. The reaction mixture is stirred for 3 hours at a temperature of about 20° C. and then hydrolysed, with care, by the addition over a period of 30 minutes of 0.5 N aqueous hydrochloric acid (500 cc), the internal temperature being maintained at about 20° C. by external cooling with a bath of cold water. The methylene chloride solution is diluted with methylene chloride (5000 cc), decanted off, washed three times with distilled water (total 3000 cc), three times with a saturated aqueous sodium bicarbonate solution (total 1000 cc), and again three times with distilled water (total 3000 cc), then dried over anhydrous sodium sulphate in the presence of decolourizing charcoal (1 g), filtered and evaporated. The residue is triturated in diethyl ether (250 cc), the resulting crystals are filtered off, washed three times with diethyl ether (total 375 cc) and dried under reduced pressure (20 mm Hg) at a temperature of about 20° C. in the presence of potassium hydroxide pellets. Methyl 5-(4-fluorobenzoyl)-thieno[2,3-b]thiophene-2-carboxylate (51.8 g), melting at 220° C., is thus obtained.

Provenance & Evidence