Visible‐Light‐Mediated Metal‐Free Hydrosilylation of Alkenes through Selective Hydrogen Atom Transfer for Si−H Activation

Abstract

Although there has been significant progress in the development of transition-metal-catalyzed hydrosilylations of alkenes over the past several decades,m etal-free hydrosilylation is still rare and highly desirable.H erein, we report ac onvenient visible-light-driven metal-free hydrosilylation of both electron-deficient and electron-richalkenes that proceeds through selective hydrogen atom transfer for Si À Ha ctivation. The synergistic combination of the organophotoredoxcatalyst 4CzIPN with quinuclidin-3-yl acetate enabled the hydrosilylation of electron-deficient alkenes by selective SiÀHa ctivation while the hydrosilylation of electron-rich alkenes was achieved by merging photoredoxa nd polarity-reversal catalysis.

Neutral‐Eosin‐Y‐Photocatalyzed Silane Chlorination Using Dichloromethane

“…[3] As silicon is more electropositive than carbon (electronegativity of 1.90 vs. 2.55 on the Pauling scale), SiÀHb onds are generally more hydridic than C À Hb onds.I nt his context, we have recently achieved av isible-light mediated hydrosilylation of both electron-deficient and electron-rich alkenes through the synergistic merger of ap hotoredox catalysts and aH AT mediator. [4] Additionally,w er ecently disclosed the unique property of neutral eosin Y, which can function as an ideal direct HATp hotocatalyst owing to its visible-light-absorption, metal-free,r eadily available,a nd low-cost nature. [5] It has been applied to the CÀHalkylation, which accommodates an extremely broad substrate scope owing to no limitation on redox potentials.…”

Visible‐Light‐Mediated Metal‐Free Difunctionalization of Alkenes with CO2 and Silanes or C(sp3)−H Alkanes

“…We envisioned that the incorporation of an electrophile such as CO 2 in the reaction mixture might enable difunctionalization of alkenes over the competing protonation, and produce b-silacarboxylic acids. [ However, the use of transition metals,s trong bases or prefunctionalized radical precursors are required in these reaction systems.A s part of our continuing interests in developing visible-lightpromoted transformations using inexpensive gaseous feedstocks [11] and readily available C(sp 3 ) À Ha nd Si À Hb onds as latent nucleophilic handles, [7,12] we herein report the first silacarboxylation of simple alkenes using CO 2 and silanes through the synergistic combination of an organic photoredox catalyst and aH AT catalyst. [8] However,c onsiderable advances of functionalization of alkenes with CO 2 are confined to hydrocarboxylation, [9] and difunctionalization of alkenes with CO 2 is quite rare.…”

Dehydrogenative Silylation of Alkenes for the Synthesis of Substituted Allylsilanes by Photoredox, Hydrogen‐Atom Transfer, and Cobalt Catalysis

“…Thee legant processes avoid the use of an oxidant and provide efficient access to CÀCand CÀXbonds. [7] To accomplish this goal, the major challenge to address is how to avoid the hydrosilylation process and vinylsilane byproducts.Herein, we report anovel tricatalytic activation method, that is,t he synergistic combination of photoredox, [8] HAT (hydrogen-atom transfer), [9] and cobalt catalysis, [6] which provides an efficient and general pathway to the selective construction of allylsilanes. In contrast to the pathways for cross-coupling between alkenes and different nucleophiles, [6j-n] we envisaged that the dehydrogenative cross C-Si coupling reaction would be highly beneficial as areliable synthetic technique.C onsidering the similar bond dissociation energy (BDE) of the SiÀHand CÀHbonds,the hydrogen abstraction process with either an electrophilic radical or radical cation can also enable the activation of aSi À Hbond.…”