General procedure for the synthesis of 4-iodo-1H-pyrrole-2-carbaldehyde from 2-pyrrolecarboxaldehyde: 1H-pyrrole-2-carbaldehyde (7.0 g, 73.6 mmol) was dissolved in tetrahydrofuran (45 mL) and the solution was cooled to -75 °C. N-iodosuccinimide (19.8 g, 88.3 mmol) was added in batches over 20 minutes, followed by continuous stirring of the reaction mixture at -75 °C for 2 hours. Upon completion of the reaction, water and petroleum ether were added and the mixture was slowly warmed to room temperature. The organic layer was separated and the aqueous phase was extracted with petroleum ether. All organic layers were combined, washed sequentially with water and brine, dried with anhydrous sodium sulfate, filtered and concentrated under vacuum to afford 4-iodo-1H-pyrrole-2-carbaldehyde (13.2 g, 81% yield) as a black solid.
