Catalytic Synthesis of Silanols from Hydrosilanes and Applications

Abstract

In recent years reusable and highly active metal-nanoparticle catalysts were developed for the selective transformation of hydrosilanes into the corresponding silanols using water as the oxidant. The catalysts are much more active than conventional homogeneous ones under ambient conditions. In this perspective, we summarize known catalyst systems as well as stoichiometric methods for the synthesis of silanols from hydrosilanes. Plausible pathways for the hydrolytic oxidation of hydrosilanes on metal nanoparticles are described on the basis of the observations of mechanistic studies, including Si−H bond activation, nucleophilic attack of water (or silanol) at the silicon bonded to metal, and the liberation of silanol (or disiloxane) products. The applications of silanols are classified into usages in organic synthesis and silicon-based materials. Silanols were employed as nucleophilic partners in transitionmetal catalyzed carbon−carbon cross-coupling reactions, organocatalysts for activating carbonyl compounds, intramolecular guiding groups for C−H bond activation reactions, inhibitors of enzymes, and isosteres of bioactive compounds. Various polymeric siliconbased materials were synthesized by the activation of Si−H bonds in bis-trihydrosilanes, bis-hydrosilanes, and polyhedral oligomeric silsesquioxanes (POSS).

Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals

“…53 Interestingly, although the synthesis of silanols from hydrosilanes have been reported using water as an oxidant, 54 the development of environmentally benign, highly selective, and practical processes for synthesizing silanols is still highly desirable. 55 In this context, Kaneda and coworkers reported a highly efficient method for the green synthesis of silanols from hydrosilanes in 2008. 56 They found that the silver nanoparticles supported on hydroxyapatite (Ag-HAp) exhibited high catalytic activities for the selective oxidation of hydrosilanes using water as a green oxidant without the use of organic solvents (Scheme 13).…”

Catalytic Reductive ortho-C–H Silylation of Phenols with Traceless, Versatile Acetal Directing Groups and Synthetic Applications of Dioxasilines

“…Interest in organosilane chemistry has increased rapidly in recent years, 1 including the development of silicon-based materials 2 and many biomedically relevant agents. 1a,3 The recent expanding use of these compounds has included their participation in a wide variety of chemical transformations.…”

“…1a,3 The recent expanding use of these compounds has included their participation in a wide variety of chemical transformations. Such synthetic activities include silicon-based cross-coupling reactions, 4 oxidations, 5 silanol hydrogen bond donor catalysts, 6 and as directing groups for C–H functionalization.…”

“…20 In these studies, we established the mechanism for the hydridosilyl O,O -silyl acetal-directed catalytic C–H silylation, where the turnover-determining step is an irreversible substrate–metal coordination that proceeds to C–H bond cleavage. 1a,21 To develop a more general catalytic method to improve arene ortho- C–H silylation of phenols, we have designed a novel approach to sequential catalytic reductive C–H silylation. This process centers on postinstallation of other useful moieties on a silicon center that includes spontaneous removal of directing groups by employing versatile silyl acetal directing groups.…”

Chlorine‐Free Catalytic Formation of Silsesquioxanes with Si‐OH and Si‐OR Functional Groups

“…The wide utility of silanols and silyl ethers requires efficient synthetic procedures from available precursors. Nowadays, the synthesis of silanols may be performed from chlorosilanes, siloxanes, or hydrosilanes via hydrolysis, nucleophilic substitution, and oxidation, respectively. The catalytic methods for Si‐H oxidation occurring in the presence of transition metals have gained much attention .…”