Isomerization of Trimethyl a-Keto Trithioorthocarboxylates into a a-Bis(methylthio)thiolcarboxylates. A New Rearrangement of Synthetic Interest

A study was made of the isomerization reaction of a great variety of trimethyl alpha-keto trithioorthocarboxylates to alpha,alpha'-bis(methylthio) thiolcarboxylates, intermediates of high synthetic value for the synthesis of R-arylpropionic acids. The reaction was carried out in methylene chloride in the presence of catalytic amounts of trityl perchlorate or methanesulfonic acid and was complete in 2 h at rt. In most of the investigated cases the result was positive, the yields usually being greater than 90%. Also the reaction mechanism was subjected to an experimental study.