Ligand-Controlled Rh(I) -Catalyzed Intramolecular Alkyne Sila-Cyclization: Divergent Catalysis and Mechanistic Studies

Abstract

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