General procedure for the synthesis of 5-(hydroxymethyl)-1H-pyrrole-2-carboxaldehyde from 1H-pyrrole-2,5-dicarboxaldehyde: Sodium borohydride (0.46 g, 12.2 mmol) was added in a single step to an anhydrous methanol (100 mL) solution of 1H-pyrrole-2,5-dicarboxaldehyde (6.0 g, 48.8 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for 30 min before the reaction was quenched with ice water and subsequently concentrated under vacuum. The resulting aqueous solution was extracted with ethyl acetate (3 x 100 mL), the organic layers were combined and washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated. The residue was purified by silica gel fast column chromatography (petroleum ether/ethyl acetate=4/1) to afford 5-(hydroxymethyl)-1H-pyrrole-2-carbaldehyde (5.92 g, 98%) as a white amorphous powder.
