Organolithium reagents disproportionation

The alkylation of tin tetrachloride with organolithium compounds, Grignard reagents, or organoaluminum compounds remains the most common route to tetraalkyltins, and thence, by the Kocheshkov disproportionation, to the various organotin halides. 

Furukawa, N. Ogawa, S. Matsumura, K. Fuji-hara, H. Extremely facile ligand-exchange and disproportionation reactions of diaryl sulfoxides, selenoxides, and triarylphosphine oxides with organolithium and Grignard reagents. 

Sulfoxides react with organolithium and Grignard reagents by four different reaction pathways. One involves nucleophilic substitution with Walden inversion at the sulfinyl sulfur atom. A second involves a concomitant ligand exchange and disproportionation reactions. A third process, recently discovered, comprises ligand coupling reactions, and the fourth is the formation of a-sulfinyl car-banions by proton abstraction. The four reactions are summarized in Scheme 4. 

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