A 4-Chloro-5-trifluoromethyl-2,2,4-trifluoro-1,3-dioxolane (1) was synthesised by reaction of CF2(OF)2 with CF3---CH=CFCl; the elimination of HCl from (1) in basic conditions led to the formation of dioxole perfluoro-4-methyl-1,3-dioxole (2). Both these synthetic steps gave the corresponding product in high yield. A new synthetic route for the preparation of CF3---CH=CFCl, starting from CF2ClBr and CH2=CF2, together with some examples of polymerisation products obtained by reaction of dioxole (2) with fluoroolefins are also reported.