Asymmetric Cyclopropylcarbinyl Cation Rearrangement Enabled by Chiral Super Brønsted C–H Acids for Stereospecific Alkene Synthesis

Comprehensive Summary The simultaneous and precise control over both alkene geometry and molecular chirality remains a formidable challenge in asymmetric synthesis, particularly within the realm of carbocation chemistry. Carbocations are notoriously difficult to tame due to their planar structure and high reactivity, which often leads to the loss of stereochemical information. Here, we report a transformative catalytic strategy that addresses this long‐standing challenge by harnessing cyclopropylcarbinyl cations as programmable intermediates under the sophisticated governance of chiral super Brønsted acids. These highly reactive cations, generated in situ via the protonation of readily available precursors, do not exist as “free” species; instead, they undergo a stereospecific ring‐opening rearrangement pathway that is precisely directed by a tightly associated chiral counteranion. This ion‐pair catalysis model effectively decouples the stereochemical outcome from inherent substrate bias or thermodynamic equilibria. By utilizing the unique structural framework of C–H acids (such as imidodiphosphorimidates), the catalyst creates a confined chiral environment where noncovalent interactions, including London dispersion and hydrogen bonding, stabilize the transition state. This level of control enables the simultaneous installation of a defined tetrasubstituted or trisubstituted carbon center and a stereodefined double bond, achieving exceptional levels of enantioselectivity and E / Z selectivity. The synthetic utility of this method is demonstrated through the direct access to valuable 1,1‐diaryl trisubstituted alkenes and complex sulfur‐containing products with high stereochemical fidelity. Unlike conventional strategies that rely on expensive transition metals or extensive pre‐functionalization of substrates, our approach leverages a classical S N 1‐type manifold. This atom‐economical process is environmentally benign, with water formed as the sole byproduct. By integrating rearrangement chemistry with the potency of super Brønsted acid catalysis, this work significantly expands the boundaries of organocatalysis. Overall, this strategy establishes a robust and general approach for the stereocontrolled synthesis of complex molecules via transient cationic intermediates, paving the way for the exploitation of high‐energy reactive species in total synthesis and medicinal chemistry.