[S:1]1[CH:5]=[CH:4][C:3]([C:6](Cl)=[O:7])=[CH:2]1.Cl.[CH3:10][NH:11][O:12][CH3:13].C(N(CC)CC)C.O>ClCCl>[CH3:13][O:12][N:11]([CH3:10])[C:6]([C:3]1[CH:4]=[CH:5][S:1][CH:2]=1)=[O:7]To a solution of this crude thiophene-3-carbonyl chloride (97.7 g, 666 mmol) and N,O-dimethylhydroxylamine hydrochloride (71.5 g, 733 mmol) in dichloromethane (600 mL) at 0° C. was added dropwise triethylamine (186 mL, 1.33 mol). After stirring at room temperature for 3 h, the reaction mixture was poured into water (2 L), the layers were separated and the aqueous layer extracted with dichloromethane (2×200 mL). The combined organic layers were washed with water (200 mL), then dried over MgSO4 and concentrated in vacuo to afford N-methoxy-N-methylthiophene-3-carboxamide [102.2 g, yield 90%; HPLC/MS: m/z=172 (M+H); log P(HCOOH)=1.30].
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