Synthesis and transformations of 1,3-dithiol-2-ylideneisopropylidene malonates

The reaction of 2-alkylthio-1,3-dithiolium salts with Meldrum's acid gave 1,3-dithiol-2-ylideneisopropylidene malonates, which were converted successively to monoethyl esters of 1,3-dithiol-2-ylidenemalonic acids and esters of 1,3-dithiol-2-ylideneacetic acid. 2-Methyl-1,3-dithiolium salts are formed when 1,3-dithiol-2-ylideneisopropylidene malonates are heated with acids.