Addition of cyclic ethers and acetals to ethyl 3,3-difluoro-2-methylpropenoate

Ethyl 3,3-difluoro-2-methylpropenoate forms 1 : 1 adducts with tetrahydrofuran and 1,3-dioxolanes under free radical conditions. In contrast no 1 : 1 adducts are observed when tetrahydropyran and 1,3-dioxanes are used as sources of α-alkoxy radicals. An explanation is presented based on FMO and radical stability arguments.