Summary Evidence is presented which indicates that pyrolysis of N-( 3-hydroxypropy1thio)phthalimide gives 1,2-oxathiolan as a volatile product via an intermediate tentatively identified as a cyclic oligomer. ... IN recent years a number of examples of cyclic sulphenic acid esters (sultenes) in which the heteroatoms are part of a five-membered ring have been described.1 In all instances however the sultene system is heavily disguised by the presence of bulky substituents ...