[CH3:1][C:2]1[C:6]([OH:7])=[C:5]([C:8]([O:10][CH:11]([CH3:13])[CH3:12])=[O:9])[S:4][C:3]=1[C:14]([O:16][CH:17]([CH3:19])[CH3:18])=[O:15].O1CCOCC1.C(=O)([O-])[O-].[K+].[K+].[CH2:32]([S:36](Cl)(=[O:38])=[O:37])[CH2:33][CH2:34][CH3:35]>CC(C)=O>[CH3:1][C:2]1[C:6]([O:7][S:36]([CH2:32][CH2:33][CH2:34][CH3:35])(=[O:38])=[O:37])=[C:5]([C:8]([O:10][CH:11]([CH3:13])[CH3:12])=[O:9])[S:4][C:3]=1[C:14]([O:16][CH:17]([CH3:19])[CH3:18])=[O:15]A mixture of 2.3 g (8 mmol) of di-isopropyl 3-methyl-4-hydroxy-2,5-thiophene-dicarboxylate, 30 ml of dioxane, 60 ml of acetone, 1.6 g (120 mmol) of anhydrous potassium carbonate and 1.6 g (10 mmol) of butane-sulfonyl chloride was refluxed for about 10 hours. The mixture was then freed from dioxane and acetone by distillation in vacuo and then added with ethylether, washed with water, and dried with anhydrous magnessium sulfate. The solvent was removed by distillation and then recrystallization was effected from methanol to give 2.8 g (86%) of the desired white crystalline compound. m.p. 59°-61° C.
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