Br[C:2]1[C:6]([CH3:7])=[CH:5][S:4][CH:3]=1.C([Li:12])CCC.[S:13](=[O:15])=[O:14]>C(OCC)C.CCCCCC>[CH3:7][C:6]1[C:2]([S:13]([O-:15])=[O:14])=[CH:3][S:4][CH:5]=1.[Li+:12]To 30 g of 3-bromo-4-methylthiophene in 150 ml of anhydrous ethyl ether under nitrogen at -70° to -75° C. was added, cautiously, during 30 minutes 111 ml of 1.6 M butyl lithium in hexane. The mixture was stirred for an additional thirty minutes and then 30 ml of liquified sulfur dioxide was added at such a rate that the temperature of the reaction mixture was maintained below -70° C. Upon completion of the addition, the mixture was stirred for an additional 90 minutes at -75° C. and then allowed to stand overnight at room temperature. The resulting precipitate was filtered and washed with ethyl ether, dried in air and in vacuo under nitrogen to yield 30 g of the desired salt, m.p. >250° C.
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