Next, the fluorination reaction was carried out with 5, where the C2 position was substituted (Figure ). As a result, only trifluoroborate salt 6 was obtained in a good yield, with no ring-opened product was obtained upon heating. When the fluorination reaction was attempted using 7, which is unsubstituted at the C3 position, one equivalent of Selectfluor ® gave the fluorinated compound 8 as the main product (50%) and the ring-opened compound 9 as a byproduct, demonstrating further fluorination. When the amount of Selectfluor ® was increased to two equivalents, 9 became the main product (58%). These results demonstrated that the ring-opening fluorination can proceed as long as an appropriate substituent is present at the C3 position.