Table 2. Reaction scope for the construction of bridged [4.2.1] lactones 2 ^a .

^aReaction conditions: 1 (0.2 mmol), HNTf₂ (0.04 mmol), DCE (4 mL), 40 °C, in vials; yields are those for the isolated products.

^b80 °C, 36 h.

^c48 h.

^d30 mol% of HNTf₂ was used, 60 °C, 24 h.