1,3,3,3-Tetrafluoro-2-methoxycarbonylpropenylsulfenyl chloride readily reacts with activated aromatic and heterocyclic compounds to form C-sultenylation products as E isomers. In some cases, its reactions with phenolic compounds are accompanied by cyclization giving rise to fused 2-(2,2,2-trifluoro-1-methoxycarbonylethylidene)-1,3-oxathioles.