Regio- and Enantioselective Palladium-Catalyzed (4 + 2) Silacycloaddition of Unsymmetrical Internal Alkynes with Racemic Benzosilacyclobutenes

Silicon-stereogenic architectures are valuable in organosilicon chemistry and medicinal chemistry, but their enantioselective synthesis via silicon-centered chirality transfer remains a challenge. In contrast to well-studied chirality-at-carbon chemistry, the construction of silicon-stereogenic centers has been considered as a challenging topic due to its limited synthetic strategy. Here, we realized a kinetic resolution process to establish a palladium-catalyzed enantioselective ring-expansion-type (4 + 2) silacycloaddition reaction of racemic benzosilacyclobutenes with unsymmetrical internal alkynes via selective Si–C(sp3) bond cleavage. By employing a chiral TADDOL-derived phosphoramidite ligand, we achieved the kinetically controlled catalytic asymmetric construction of silicon-stereogenic benzo[c]silin derivatives with good enantioselectivity. The catalytic system features mild conditions, high chemoselectivity, a broad substrate scope, and good functional group tolerance, demonstrating broad applicability to unsymmetrical alkynes bearing terminal ketone or ester groups. Furthermore, the kinetic studies of racemic substrates corroborate the versatility and applicability of this strategy, offering a robust strategy called the kinetic resolution of racemic substrate in this work to access structurally diverse silicon-stereogenic organosilicon compounds.