Studies on sulfinatodehalogenation. XX. Sodium dithionite‐initiated addition of per‐ and polyfluoroalkyl iodides to cyclic enol ethers and chemical conversions of the products

Per‐ and polyfluoroalkyl iodides [R F I, R F =Cl(CF 2 ) 4 , 1a ; Cl(CF 2 ) 6 , 1b ; Cl(CF 2 ) 8 , 1c ; n ‐C 6 F 13 , 1d ; n ‐C 8 F 17 , 1e ] reacted with cyclic enol ethers such as 2,3‐dihydrofuran (2) and 3,4‐dihydro‐2 H ‐pyran (3) in aqueous acetonitrile in the presence of sodium dithionite and sodium bicarbonate at room temperature (10–15°C) to give the corresponding 2‐( F ‐alkyl) hemiacetals in high yields. The adducts were oxidized with Ce(NH 4 ) 2 (NO 3 ) 6 in acetonitrile or reduced with LiAlH 4 in ether to form the corresponding 2‐( F ‐alkyl)lactones or diols respectively in good yields. In the presence of p ‐toluenesulfonic acid, the adducts were refluxed in benzene and CH 3 CN to produce the corresponding 2,3‐dihydro‐4‐( F ‐alkyl) furan and 3,4‐dihydro‐5‐( F ‐alkyl)‐2 H ‐pyran. This is a new and effective method for preparing these useful organofluorine compounds.