Table . Substate Scope of Silyl dienol ethers and BCBs a a Reaction conditions: unless indicated otherwise, the reaction of silyl enol 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. b the reaction was run in the presence of Sc(OTf)3 (0.02 mmol) at room temperature for 30 min. The yield was of isolated and purified products.