Bicyclo[1.1.0]butanes could be activated as an enolate nucleophile upon central -bond cleavage mediated by Lewis acid to attack electrophilic reagents such as aryl aldimine by Leitch group, 8a aldehyde by Glorius group, 8c or ketene by Studer group, 8b followed by the intramolecular cyclization to complete the formal cycloadditions. We demonstrated that Lewis acid could activate BCBs as electrophiles to react with indoles as the nucleophiles to construct complex indoline polycycles (Scheme 1b-2). Notably, if a wide variety of nucleophiles could be utilized, this approach could be developed into a versatile strategy that complements existing methods involving radical or ionic intermediates to access BCHs. More recently, Feng reported the use of silver triflate to promote reactions of BCBs and indoles but with opposite regioselectivity. 8e Despite these successful examples, there is a huge and unexplored chemical space for these bicycles, and a more general strategy to expediently construct such moieties with simple alkenes could potentially be realized. Here, we envisaged that the silyl enol ether, as the nucleophile, would be a suitable candidate in this scenario due to its importance in different cycloaddition reactions. It is noteworthy that silyl enol ethers could be easily prepared by a one-step silylation of simple ketone motifs, which are presented in numerous compounds and widely used in synthetic chemistry. Although silyl enol ethers exhibit robust nucleophilicity in various synthetic contexts, such as Mukaiyama-Aldol reaction and Michael addition, their nucleophilicity towards the BCB remains unexplored. Furthermore, the subsequent intramolecular Aldol-type cyclization presents a challenge due to the formation of sterically hindered vicinal quaternary carbon centers. Despite these concerns, we aim to explore the formal [2+3] cycloaddition between silyl enol ether and BCB to realize a one-step access to a variety of BCH frameworks. a Reaction conditions: unless indicated otherwise, the reaction of silyl enol ether 1 (0.1 mmol), and BCB 2 (0.13 mmol) was carried out in solvent (1 mL) in the presence of Lewis acid (0.01 mmol) at room temperature for 2-6 h. b Yields were determined by 1 H NMR analysis of the unpurified reaction mixture with 1,1,2,2-tetrachloroethane or 1,3,5-trimethoxybenzene as an internal standard. The yield of the reaction with 5 mol% of Yb(OTf)3. n.r., no reaction.