Ligand-controlled Rh(i)-catalyzed intramolecular alkyne sila-cyclization: divergent catalysis and mechanistic studies

Abstract

The synthesis of structurally diverse silacycles is crucial for silicon-containing drug and agrochemical development. However, catalytic synthesis of dense-functionalized silacycles based on selective cleavage and reconstruction of the carbon–silicon bond in organosilicon precursors remains largely elusive. Herein, we report divergent catalysis of ring-reconstruction transformation of silacycles based on rhodium-catalyzed Si–C bond cleavage, wherein the cyclic silylmetal intermediates undergo highly efficient and novel intramolecular Si–C bond-forming reactions under mild conditions. Under the ligand-controlled Rh-catalyzed intramolecular silacyclization process, two different pathways of new Si–C bond-forming transformations were established through intramolecular sila-cyclization reaction between alkyne moieties and silacyclobutane moieties, resulting in structurally diverse chromane-like silacycles. Furthermore, DFT calculations confirmed that bulky P-ligand P5 and the TADDOL-derived phosphonite ligand L1 played different roles in controlling the reaction pathways in the Rh-catalyzed intramolecular silacyclization and subsequent olefin migration process.