The spectral data match literature . 20 1.0 eq . ) in dry DCM ( 10 mL ) at 0 ° C . After complete addition , the cooling bath was removed and the mixture was allowed to stir at room temperature overnight . The volatiles were removed under reduced pressure , water ( 15 mL ) was added carefully ( cooling ) to the residue followed by NaOH pellets ( 1.97 g , 49.2 mmol , 8.0 eq . ) and the mixture was stirred at room temperature for 6 h , heated to reflux for 30 min and stirred overnight at room temperature . EtOAc ( 40 mL ) was added , the phases were separated and the aqueous layer was extracted with EtOAc ( 2 x 10 mL ) . The combined organic extracts were dried over Na2SO4 and evaporated . The crude was purified by automated flash chromatography ( EA : Hx , 0 à 10 % EA ) with 4 - ethyl-1H - pyrrole-2 - carbaldehyde ( S7 ) eluting at 8 % EA ( yellow - brownish oil ( 139 mg , 1.13 mmol , 18 % ) ) and 3 - ethyl-1H - pyrrole-2 - carbaldehyde ( S8 ) eluting at 10 % EA ( faintly yellow oil ( 295 mg , 2.40 mmol , 39 % ) ):