Catalytic asymmetric activation of bicyclobutanes

The precise manipulation of unfunctionalized hydrocarbons remains a fundamental challenge for chemical synthesis and catalysis. Stereodifferentiation in strained alkanes is particularly difficult to accomplish because a catalyst has to distinguish various highly exergonic chemo- and stereoselective strain-release channels. Here we disclose an organocatalytic asymmetric hydroalkoxylation of bicyclobutanes with alcohols to efficiently access tertiary cyclopropylcarbinyl ethers with high enantioselectivity (e.r. up to 98:2). Enantiocontrol is accomplished through chiral recognition between the confined iminoimidodiphosphoric acid catalyst and the substrate, mediated by non-covalent interactions between a Lewis basic binding site of the confined anion and the polarized C–H bond of the cyclopropylcarbinyl ion intermediate. Our work establishes bicyclobutane activation by harnessing strain-release energetics while maintaining precise stereo- and regiocontrol through structural confinement.