Development of an organosilica material containing ordered triene coordination sites and its application in borylation of aryl iodides

Abstract

An organosilica material containing conjugated triene moieties (triene-SiO₂-TMS; TMS = trimethylsilyl) was developed. The structure of triene-SiO₂-TMS was characterized by nitrogen adsorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM) to reveal that triene-SiO₂-TMS consists of organosilica particles with a molecular-scale ordered arrangement of conjugated triene moieties on the surface. Treatment of triene-SiO₂-TMS with commercially available Pd(dba)₂ in THF at ambient temperature afforded Pd-triene-SiO₂-TMS, in which Pd was immobilized on the surface. Pd-triene-SiO₂-TMS exhibited catalytic activity towards the borylation of aryl iodides with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin). The reactions proceeded without the addition of exogenous ligands such as phosphines. The catalyst exhibited good functional group compatibility including electron-withdrawing and -donating functional groups. The recyclability of Pd-triene-SiO₂-TMS was examined to demonstrate its moderate reusability.