Intermolecular Formal [2π+2σ] Cycloaddition of Enol Silyl Ethers with Bicyclo[1.1.0]butanes Promoted by Lewis acids

A new approach to directly access bicyclo[2.1.1]hexanes (BCHs) from easily prepared enol silyl ethers and bicyclo[1.1.0]butanes (BCBs) through formal [2π+2σ] cycloaddition was developed involving two-electron mediated process promoted by commercially available Lewis acids. This new reaction tolerated a wide range of enol silyl ethers and BCBs. In addition, a scale-up experiment and the synthetic transformations of the cycloadducts further highlighted the synthetic utility.