A study was made of the isomerization reaction of a great variety of trimethyl α-keto trithioorthocarboxylates to α, α-bis (methylthio) thiolcarboxylates, intermediates of high synthetic value for the synthesis of α-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 ...