Original reactions of α,α-dithio aryl alkanes with butyllithiums

Thioacetals derived from aromatic ketones react with butyllithiums already at -78°C and produce via a reductive process the corresponding α-thiobenzyllithiums in high yields. The same reaction also takes place selectively, under suitable conditions, with the thioacetals derived from benzaldehyde on which a competing metallation reaction is also possible. These observations clearly show that the thioacetal functionality is not a suitable protecting group against alkyllithiums for aromatic carbonyl compounds.