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 1.6M 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.