General procedure for the synthesis of 4-iodothiophene-2-carbaldehyde using 2-(4-bromothiophen-2-yl)-1,3-dioxolane as starting material: 2-(4-bromothiophen-2-yl)-1,3-dioxolane (8.02 g, 34 mmol) was dissolved in anhydrous ethyl ether (150 mL), and cooled to -78°C. A hexane solution of 2.5 M n-butyllithium (16.3 mL, 41 mmol) was slowly added dropwise with stirring, and stirring was continued for 20 min after completion of the drop. Subsequently, an anhydrous ether solution (50 mL) of iodine (8.64 g, 34 mmol) was added slowly dropwise, and the solution gradually turned red during the dropwise addition. After the dropwise addition, the reaction mixture was slowly warmed up to room temperature and stirring was continued for 20 min. The reaction was quenched by the addition of 1N hydrochloric acid solution (100 mL) and stirred overnight. After completion of the reaction, the reaction mixture was diluted with ethyl acetate and partitioned with deionized water. The organic phase was dried with anhydrous magnesium sulfate and concentrated under reduced pressure to remove the solvent to give a yellow oily product (7.0 g, 87% yield). The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-D6): δ 8.10 (d, J = 1.32 Hz, 1H), 8.33 (t, J = 1.22 Hz, 1H), 9.90 (d, J = 1.32 Hz, 1H).
