1,1-Dichloroethane → 3,5-Dimethyl-1H-pyrrole-2-carbaldehyde
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Cl[CH:2](Cl)[CH3:3].P(Cl)(Cl)(Cl)=[O:6].[CH3:10][C:11]1[NH:12]C=[C:14]([CH3:16])[CH:15]=1>CN(C)C=O>[CH3:10][C:11]1[NH:12][C:2]([CH:3]=[O:6])=[C:14]([CH3:16])[CH:15]=1Cl[CH:2](Cl)[CH3:3].P(Cl)(Cl)(Cl)=[O:6].[CH3:10][C:11]1[NH:12]C=[C:14]([CH3:16])[CH:15]=1>CN(C)C=O>[CH3:10][C:11]1[NH:12][C:2]([CH:3]=[O:6])=[C:14]([CH3:16])[CH:15]=1To a solution dimethylformamide (80.4 g) and 1 L of dichloroethane at 0° C. was added phosphorous oxychoride (153.3 g) over a few minutes and the reaction stirred for 1–2 hr at 0° C. 2,4-Dimethylpyrrole (114.6 g) was added dropwise to the above solution at temperature below 5° C. After the addition was complete the reaction was heated and the aqueous layer isolated and saved. The organic layer was extracted again with 300 mL of water and the two aqueous layers combined. The aqueous phase was extracted with 200 mL of dichloroethane and the organic layer discarded. The aqueous phase was cooled to 10° C. and adjusted to pH 10 with 10% sodium hydroxide. The mixture was stirred at 10° C. for 2 hr. The yellow solid was collected by vacuum filtration and washed thoroughly with water. The solid was dried at room temperature under vacuum to give 110.8 g (90% yield of 2,4-dimethyl-5-formylpyrrole.
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