Fig. 3: Substate scope of silyl dienol ethers and BCBs.

^aReaction conditions: unless indicated otherwise, the reaction of silyl dienol ether 1 (0.2 mmol), and BCB 2 (0.26 mmol) was carried out in DCM (2 mL) or toluene (2 mL) in the presence of Yb(OTf)₃ (0.01 mmol) at room temperature for 3 h. The yield was of isolated and purified products. ^bThe reaction was run in the presence of Sc(OTf)₃ (0.02 mmol) at room temperature for 30 min. rr: regioselectivity ratio of (4 + 3) to (3 + 2) cycloadduct. Naph 2-naphthyl, TIPS triisopropylsilyl.