Under N2 atmosphere, n-BuLi (2.67 M solution in hexane, 2.9 mL, 7.5 mmol) and N,N,N′,N′tetramethylethylenediamine (1.1 mL, 7.5 mmol) was added in dry hexane (7.5 mL) and stirred for 10 min at room temperature. The resultant solution was added thiophene (0.27 mL, 3.4 mmol), and stirred at 50 °C for 1 hour. The resultant light-yellow suspended solution was cooled to 0 °C, and then added dropwise 5-formylthiophene-2carbonitrile (0.929 mg, 6.7 mmol) in THF (7.5 mL). The resultant solution was stirred for 15 min at 0 °C, and then 1 hour at room temperature. The resultant solution was quenched by saturated aq. NH4Cl. The product was extracted with EtOAc, and then the organic layer was washed with water (×1) and brine (×1), and then dried over Na2SO4. Solvent was removed under the reduced pressure. The crude product was purified by column chromatography (silica gel, hexane/EtOAc 1:1). A fraction containing the desired product was concentrated under vacuum to give the title compound as yellow oil (642.9 mg, 1.90 mmol, 53%). The NMR analysis suggested that 2c was obtained as a mixture of diastereomers. Rf = 0.20 (hexane/EtOAc 1:1);