Alkylation at sulfur atoms

The formation of S-alkyl thiocarbamates was studied from fundamental and applied viewpoints. These compounds represent an important synthetic target due to their pesticide properties. The conventional method implies the alkylation of sodium thiocarbamates by alkyl chlorides (Eq. 58). This lengthy reaction requires heating but the thermally unstable products suffer partial 

138 Whitfield, D.M. Meah, M.Y. Krepinsky, J.J. Collect. Czech. Chem. Commun. 1993, 58, 159-172. 

In every case, the ultrasonic procedure provides the product in higher yield and purity. A kinetic study reveals a complex behavior, which can be explained, according to the authors, if the mechanism implies a radical intermediate formed by the sonolysis of one of the initial compounds. It can be observed, however, that S-alkylation reactions with alkyl chloride probably follow a polar mechanism.  

Other cases of alkylation of thiols were studied. Dithiols can be alkylated by halocarboxylic acids in high yields imder ultrasonic PTC conditions, but details are not readily available.  

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