Quinones. Part 10. Side-chain methylthiolation of methylbenzoquinones

Abstract

2,3,5,6-Tetramethylbenzoquinone undergoes side-chain reaction with excess of sodium methanethiolate to form mono-, di-, and tri-methylthiomethyl derivatives in low yields. 2,5- and 2,6-Dimethylbenzoquinones react first on the nucleus to give dimethyl(dimethylthio)quinones followed by limited side-chain methylthiolation. The sidechain reaction is restricted by a competing redox reaction. The presence of semiquinone radical anions can be detected by selective line-broadening in the n.m.r. spectra of quinone–thiolate solutions.