Asymmetric Dearomative Dual-Functionalization via Rearomatization-Blocked Sulfonium Claisen Rearrangement

The aromatic Claisen rearrangement transiently generates dearomatized intermediates that are generally too unstable to be intercepted and thus undergo spontaneous rearomatization. In this study, we demonstrate that this otherwise inevitable rearomatization can be effectively suppressed, thereby enabling asymmetric dearomative dual functionalization. Specifically, we have developed an asymmetric dehydrative rearrangement of chiral aryl sulfimides that proceeds at exceptionally low temperature (-95 °C), providing a unique window to intercept the highly unstable dearomatized intermediates in situ. A wide array of nucleophiles-including enol silyl ethers, organozinc reagents, and heteroatom nucleophiles-proved competent in capturing these intermediates, affording dual-functionalized dearomatization products with up to four contiguous stereocenters. Remarkably, these dearomatization products undergo three distinct desulfurization pathways, furnishing structurally diverse chiral products featuring both axial and point chirality. Computational studies reveal the mechanistic divergence from the conventional rearomatization pathway to the present dearomatization manifold and uncover the origin of the high fidelity in continuous chirality transfer.