BENZO[B]THIOPHENE-3-CARBONITRILE

5381-20-4

24434-84-2

General procedure for the synthesis of benzo[b]thiophene-3-carbonitrile from 3-formylbenzothiophene: To a premixed mixed solution of hexafluoroisopropanol (HFIP) and acetonitrile (ACN) (2.0 mL, 1:1) under nitrogen protection was added aromatic aldehyde 1 (0.500 mmol, 1.0 equiv.) and trimethylsilyl azide (TMSN3; 115 mg, 1.00 mmol, 2.0 equiv). Subsequently, trifluoromethanesulfonic acid (TfOH; 17.7 μL, 0.200 mmol, 0.40 eq.) was added to two dry vials, and exothermic and rapid foaming phenomena due to gas production were immediately observed. The vial was quickly capped and the reaction mixture was stirred at room temperature for 20 to 75 min. Upon completion of the reaction, the reaction mixture was concentrated under nitrogen atmosphere. The obtained residue was suspended in a solvent mixture of dichloromethane (CH2Cl2) and hexane and loaded through a sample cassette containing 5 g silica gel. Purification was carried out by normal-phase silica gel fast column chromatography using a CombiFlash purification system, and suitable elution fractions were collected and concentrated to give the target product benzo[b]thiophene-3-carbonitrile (2).