CN(C)[CH:3]=[O:4].P(Cl)(Cl)(Cl)=O.[CH3:11][C:12]1[NH:13][CH:14]=[C:15]([CH3:17])[CH:16]=1.C([O-])(=O)C.[Na+]>ClCCCl.O.C(Cl)Cl>[CH:3]([C:14]1[NH:13][C:12]([CH3:11])=[CH:16][C:15]=1[CH3:17])=[O:4]
To dimethylformamide (4.5 mL, 57.8 mmol) under argon at 0° C. was added phosphorus oxychloride (57.8 mmol) dropwise over 5 min. The cooling bath was removed and after 15 min. 1,2-dichloroethane (15 mL) was added. The reaction mixture was again cooled to 0° C. and a solution of 2,4-dimethylpyrrole (52.6 mmol) in 1,2-dichloroethane (15 mL) was added dropwise over 15 min. The reaction was heated to reflux for 15 min, and then cooled to rt. A solution of sodium acetate (24 g) in water (75 mL) was added slowly to the reaction mixture and the resulting mixture was again heated to reflux for 20 min. After the reaction mixture was cooled to rt it was diluted with CH2Cl2, and the aqueous phase was washed with CH2Cl2 (2×50 mL). The combined organic fractions were washed with saturated NaHCO3, dried (Na2SO4), and concentrated in vacuo. The crude material was purified by chromatography on silica gel eluting with 10% ethyl acetate in hexane to provide 5.2 g (80%) of the desired compound 2-formyl-3,5-dimethylpyrrole. [M+H]+=124.1, [M−H]−=122.0
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