Visible-Light-Induced Photoredox 1,2-Dialkylation of Styrenes with α-Carbonyl Alkyl Bromides and Pyridin-1-ium Salts.

A visible-light-driven photoredox dialkylation of styrenes with α-carbonyl alkyl bromides and pyridin-1-ium salts for the synthesis of polysubstituted 1,4-dihydropyridines is reported. This reaction enables the formation of two new C(sp3)-C(sp3) bonds in a single reaction step and provides a strategy that employs pyridin-1-ium salts as the functionalized alkylating reagents via dearomatization to directly trap the resulting alkyl radicals from radical addition of alkenes and then terminate the alkene dialkylation.

Nickel-Catalyzed Reductive Cross-Coupling of Propargylic Acetates with Chloro(vinyl)silanes: Access to Silylallenes.

Because of their various reactivities, propargyl acetates are refined chemical intermediates that are extensively applied in pharmaceutical synthesis. Currently, reactions between propargyl acetates and chlorosilanes may be the most effective method for synthesizing silylallenes. Nevertheless, owing to the adaptability and selectivity of substrates, transition metal catalysis is difficult to achieve. Herein, nickel-catalyzed reductive cross-coupling reactions between propargyl acetates and substituted vinyl chlorosilanes for the synthesis of tetrasubstituted silylallenes are described. Therein, metallic zinc is a crucial reductant that effectively enables two electrophilic reagents to selectively construct C(sp2)-Si bonds. Additionally, a Ni-catalyzed reductive mechanism involving a radical process is proposed on the basis of deuteration-labeled experiments.

Iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer and hydrogen atom transfer.

Site selective functionalization of inert remote C(sp3)-H bonds to increase molecular complexity offers vital potential for chemical synthesis and new drug development, thus it has been attracting ongoing research interest. In particular, typical ß-C(sp3)-H arylation methods using chelation-assisted metal catalysis or metal-catalyzed oxidative/photochemical in situ generated allyl C(sp3)-H bond processes have been well developed. However, radical-mediated direct ß-C(sp3)-H arylation of carbonyls remains elusive. Herein, we describe an iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer (XAT) and hydrogen atom transfer (HAT). The method involves diethylaminoethyl radical-mediated generation of an aryl radical intermediate via XAT, then directed 1,5-HAT to form the remote alkyl radical intermediate and radical-radical coupling with cyanoarenes, and is applicable to a broad scope of unactivated remote C(sp3)-H bonds like ß-C(sp3)-H bonds of o-iodoaryl-substituted alkanones and α-C(sp3)-H bonds of o-iodoarylamides. Experimental findings are supported by computational studies (DFT calculations), revealing that this method operates via a radical-relay stepwise mechanism involving multiple SET, XAT, 1,5-HAT and radical-radical coupling processes.

Cobalt-Promoted Electroreductive Cross-Coupling of Prop-2-yn-1-yl Acetates with Chloro(vinyl)silanes.

An electroreductive cross-coupling of prop-2-yn-1-yl acetates with chloro(vinyl)silanes for producing tetrasubstituted silylallenes is developed. The method enables the formation of a new C─Si bond through the cathodic reduction formation of the silyl radical, radical addition across the C≡C bond, the alkenyl anion intermediate formation, and deacetoxylation and represents a mild, practical route to the synthesis of silylallenes. Mechanistic studies reveal that CoCl2 acts as the mediator to promote the formation of the alkenyl anion intermediate via electron transfer.

Palladium-Catalyzed ß-C(sp3)-H Arylation of Silyl Prop-1-en-1-ol Ethers with Aryl Halides: Entry to α,ß-Unsaturated Ketones.

A palladium(0)-catalyzed ß-C(sp3)-H arylation of silyl prop-1-en-1-ol ethers with aryl halides for the synthesis of α,ß-unsaturated ketones is presented. In contrast to the reported ß-C(sp3)-H arylation of ketones, the chemoselectivity of this current method relies on the Pd(0) catalytic systems and reaction temperatures: While using the Pd(dba)2/DavePhos/KF system at 80 °C resulted in ß-C(sp3)-H monoarylation to produce ß-monoarylated α,ß-unsaturated ketones, harnessing the Pd(OAc)2/t-Bu XPhos/K2HPO4 system at 110 °C induced ß-C(sp3)-H diarylation to afford ß,ß-diarylated α,ß-unsaturated ketones. The method provides a versatile route that uses readily available ketone-derivatized α-nonsubstituted silyl prop-1-en-1-ol ethers as the alkene sources and is characterized by a good functional group compatibility, a broad substrate scope, and an excellent selectivity.

Merging Photoredox/Nickel Catalysis for Cross-Electrophile Coupling of Aziridines with Pyridin-1-ium Salts via Dearomatization.

Merging photoredox/nickel catalysis enabling the cross-electrophile coupling of aziridines with pyridin-1-ium salts involving dearomatization for the synthesis of ß-(1,4-dihydropyridin-4-yl)-ethylamines, especially including bioactive motif-based analogues, is described. This method allows incorporation of a 1,4-dihydropyridin-4-yl group and formation a N-H amino group to construct highly valuable ß-(1,4-dihydropyridin-4-yl)-ethylamine frameworks in a single step through the C2-N bond regioselective cleavage and dearomatization alkylation cascades with precise regioselectivity and excellent functional group tolerance, and represents an appealing cross-electrophile coupling strategy to accomplish transformations between two electrophiles, including aziridines and pyridin-1-ium salts, by avoiding prefunctionalization.

Histone deacetylase 3 promotes innate antiviral immunity through deacetylation of TBK1.

TANK-binding kinase 1 (TBK1), a core kinase of antiviral pathways, activates the production of interferons (IFNs). It has been reported that deacetylation activates TBK1; however, the precise mechanism still remains to be uncovered. We show here that during the early stage of viral infection, the acetylation of TBK1 was increased, and the acetylation of TBK1 at Lys241 enhanced the recruitment of IRF3 to TBK1. HDAC3 directly deacetylated TBK1 at Lys241 and Lys692, which resulted in the activation of TBK1. Deacetylation at Lys241 and Lys692 was critical for the kinase activity and dimerization of TBK1 respectively. Using knockout cell lines and transgenic mice, we confirmed that a HDAC3 null mutant exhibited enhanced susceptibility to viral challenge via impaired production of type I IFNs. Furthermore, activated TBK1 phosphorylated HDAC3, which promoted the deacetylation activity of HDAC3 and formed a feedback loop. In this study, we illustrated the roles the acetylated and deacetylated forms of TBK1 play in antiviral innate responses and clarified the post-translational modulations involved in the interaction between TBK1 and HDAC3.

Visible light photoredox alkylazidation of alkenes with sodium azide and heteroarenium salts: entry to azido-containing 1,4-dihydropyridines.

A three-component alkene alkylazidation using sodium azide as the azido resource and heteroarenium salts as functionalized alkyl reagents for producing highly valuable 2-azido-1-(1,4-dihydropyridin-4-yl)-ethanes is described. This reaction allows the incorporation of both an azido group and a 1,4-dihydropyridin-4-yl group across C[double bond, length as m-dash]C bonds to construct two new bonds in a single reaction step, and represents a practical and mechanistically distinct alternative that harnesses an electrophilic heteroarenium ion to accomplish the alkene difunctionalization reaction.