Cross coupling reactions for carbon-carbon and carbon-heteroatom bond formation are of great importance in modern chemical synthesis. In addition to classical cross couplings involving preformed or preactivated coupling partners, more recently breakthroughs have been made in the selective, direct coupling of abundant aliphatic carbon-hydrogen bonds using hydrogen atom transfer reactions in which the bond dissociation energy is the thermodynamic driving force. The more challenging carbon-carbon bond activation is still rather underdeveloped due to the bond inertness. Herein, we report a mild and general strategy for the activation of a diverse set of readily available cyclic alcohols for the remote and site-specific arylation of ketones via the combination of photoredox-mediated multi-site concerted proton-electron transfer (MS-PCET) and nickel catalysis. The current cross coupling proceeds with the generation of an alkoxy radical utilizing bond dissociation free energy (BDFE) as the thermodynamic driving force. Subsequently, the resulting remote carbon-centered radicals formed by C-C cleavage merge with the nickel catalytic cycle to create the challenging C(sp 3 )-C(sp 2 ) bonds. Fig. 7. (A) 1 H NMR spectra of substrate 1-([1,1'-biphenyl]-4-yl)cyclohexan-1-ol in C6D6 with various amounts of collidine. (B) Longrange MS-PCET enabled cross coupling with linear alcohols. CONCLUSIONSIn summary, we have developed a robust method for the remote site-specific arylation of ketones from easily accessible tertiary alcohols through a photoredox-enabled MS-PCET and nickel catalysis. The use of a strongly oxidizing acridinium photocatalyst was critical in achieving high reaction efficiency. Thus, a variety of cyclic, linear as well as bridged alcohols can be effectively applied in this new C-C bond cleaving cross coupling procedure. We believe that further advances can be expected by applying this strategic design to other types of visible light mediated cross couplings via the C-C bond cleavage. ■ ASSOCIATED CONTENT *Supporting InformationExperimental and computational details, full characterization of the products and spectra, Cartesian coordinates of the optimized geometries.

Metal-catalyzed cross-electrophile couplings have become a valuable tool for carbon-carbon bond formation. This minireview provides a comprehensive overview of the recent developments in the topical field of cross-electrophile couplings, provides explanations of the current state-of-the-art, and highlights new opportunities arising in the emerging fields of photoredox catalysis and electrochemistry.

Trametes villosa Laccase (TVL) was immobilized through physical adsorption on SBA-15 mesoporous silica and the immobilized TVL was used in the oxidative coupling of trans-resveratrol. Higher loading and activity of the immobilized enzyme on SBA-15 were obtained when compared with the free enzyme. The effects of reaction conditions, such as buffer type, pH, temperature and substrate concentration were investigated, and the optimum conditions were screened and resulted in enzyme activity of up to 10.3 μmol/g·h. Furthermore, the oxidative couplings of the derivatives of trans-resveratrol were also catalyzed by immobilized TVL. The immobilized TVL was recyclable and could maintain 78% of its initial activity after reusing it four times.

The first metal-free ring opening / trifluoromethylthiolation of cycloalkanols for the formation of remote C(sp 3 )-SCF3 bonds has been developed. A variety of trifluoromethylthiolated carbonyl compounds, that are otherwise difficult to achieve, were prepared in good yields under mild reaction conditions. The reaction is assumed to proceed via C-C bond cleavage of the alkoxyl radical species generated via a photoredox enabled intramolecular proton-coupled electron transfer (PCET) process, followed by trifluoromethylthiolation of the resulting C-centered radical with the electrophilic N-(trifluoromethylthio)phthalimide reagent.

In the biosynthesis sterols an enzyme-catalyzed demethylation is achieved via a stepwise oxidative transformation of alcohols to olefins. The overall demethylation proceeds through two sequential monooxygenation reactions and a subsequent dehydroformylative saturation. To mimic the desaturation processes observed in nature, we have successfully integrated photoredox proton-coupled electron transfer (PCET) and cobaloxime chemistry for the acceptorless dehydrogenation of alcohols. The state-of-the-art remote and precise desaturation of ketones proceeds efficiently through the activation of cyclic alcohols using bond-dissociation free energy (BDFE) as thermodynamic driving force. The resulting transient alkoxyl radical allows C-C bond scission to generate the carbon-centered radical remote to the carbonyl moiety. This key intermediate is subsequently combined with cobaloxime photochemistry to furnish the alkene. Moreover, the mild protocol can be extended to desaturation of linear alcohols as well as aromatic hydrocarbons. Application to bioactive molecules and natural product derivatives is also presented.