[CH3:1][O:2][C:3]([C:5]1[S:6][CH:7]=[C:8]([CH3:11])[C:9]=1[Cl:10])=[O:4].S(Cl)([Cl:15])(=O)=O>C(Cl)(Cl)(Cl)Cl.C(OOC(=O)C1C=CC=CC=1)(=O)C1C=CC=CC=1>[CH3:1][O:2][C:3]([C:5]1[S:6][CH:7]=[C:8]([CH2:11][Cl:15])[C:9]=1[Cl:10])=[O:4]To 2-methoxycarbonyl-3-chloro4-methylthiophene (100 g, 0.53 mol) in dry carbon tetrachloride (1.5 L) were added sulfuryl chloride (65 mL, 0.81 mol) and benzoyl peroxide (2.5 g, 10 mmol). The reaction was heated at reflux for 17 hours, then cooled to ambient temperature and concentrated of all volatiles in vacuo. Purification of the resulting oil by flash chromatography on silica gel afforded 63 g (54% yield) of 2-methoxycarbonyl-3-chloro-4-(chloromethyl)thiophene as a yellow oil which crystallized to fine needles upon standing; NMR (CDCl3) 7.6 (s,1), 4.6 (s, 2), 3.9 (s, 3) ppm.
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