Synthesis of trimethyl a-Keto Trithioorthoesters and Dimethyl a-Keto dithioacetals by reaction of esters with tris(methylthio)methyllithium

A complete study has been made of the reaction of tris(methylthio)methyllithium with aromatic, heteroaromatic, and aliphatic esters. It is a one-pot reaction that despite its complexity, and depending on the reagent ratios, the reaction conditions, and the possible use of additional reagents (N-(methylthio)phthalimide or BuLi), can supply easily, in excellent and reproducible yields, the trimethyl a-keto trithioorthoesters 3 or, alternatively, the dimethyl a-keto dithioacetals 4. The reaction mechanism has been elucidated.