Sulfur Dioxide → Lithium 4-methyl-3-thiophenesulfinate

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.