To a solution of 8-bromo-N-(2,4-difluorophenyl)-N-methyl-4H-thieno[3,2-c]chromene-2-carboxamide 160bp (19.6 mg, 0.0449 mmol, 1 equiv) in tetrahydrofuran (1 mL) at −78° C. was added n-butyllithium (54 μL, 0.14 mmol, 3.0 equiv, 2.5 M in hexanes) dropwise. After 15 min, N,N-dimethylformamide (35 μL, 0.45 mmol, 10 equiv) was added. After 40 min, the reaction mixture was warmed to 24° C. for 50 min. Saturated aqueous ammonium chloride solution (5 mL) was added to the reaction mixture, and the resulting solution was extracted with ethylacetate (3×3 mL). The collected organic was dried over anhydrous sodium sulfate, filtered, and concentrated to afford the corresponding aldehyde, N-(2,4-difluorophenyl)-8-formyl-N-methyl-4H-thieno[3,2-c]chromene-2-carboxamide. LCMS (ESI) m/z: 386.
