The wide applicability in various fields enables development of novel methods to access axially chiral styrenes to be of significance. Among the developed and potential synthetic strategies for this type of framework, the route based on an asymmetric radical process is more challenging and has not been achieved so far. Here we report a photo-promoted, three-component, asymmetric free radical reaction of potassium alkyltrifluoroborates, potassium metabisulfite, and 1-alkynylnaphthalen-2-ols, delivering axially chiral ( S , E )-1-(1-(alkylsulfonyl)-2-vinyl)naphthalen-2-ols with excellent enantioselectivity (93%–99% enantiomeric excess) and good yield (up to 97%). The transformation involves in situ generation of alkylsulfonyl radicals, tandem enantioselective radical addition, and a reduction process of radical species. • Photoinduced asymmetric catalytic radical approach to access axially chiral styrenes • A rare success in the field of asymmetric sulfur dioxide insertion • Broad substrate scope with excellent enantioselectivity and regioselectivity Development of new pathways for generation of axially chiral styrenes has gained great attention in recent years because of the wide applicability of axially chiral styrenes in chiral ligands, catalysts, and functional materials. Among the developed and potential synthetic strategies for synthesis of axially chiral styrenes, the synthetic route through an asymmetric radical process is more challenging and has not been achieved so far. Here we developed a photoinduced asymmetric catalytic radical approach to access sulfonyl-containing axially chiral styrenes with excellent enantioselectivity, regioselectivity, good yield, and broad substrate scope. Control experiments and DFT calculations were carried to understand the mechanism and the origin of the high enantioselectivity and Z/E selectivity of the reaction. Photoinduced three-component asymmetric free radical reaction of potassium alkyltrifluoroborates, potassium metabisulfite and 1-alkynylnaphthalen-2-ols, delivering axially chiral ( S , E )-1-(1-(alkylsulfonyl)-2-vinyl)naphthalen-2-ols with excellent enantioselectivity (93%–99% ee) and good yield (up to 97%). The transformation involves in situ generation of alkylsulfonyl radicals and a tandem enantioselective radical addition process. 

Access to axially chiral styrenes via a photoinduced asymmetric radical reaction involving a sulfur dioxide insertion

C(sp3) radicals (R˙) are of broad research interest and synthetic utility. This review collects some of the most recent advancements in photocatalytic R˙ generation and highlights representative examples in this field. Based on the key bond cleavages that generate R˙, these contributions are divided into C–H, C–C, and C–X bond cleavages. A general mechanistic scenario and key R˙-forming steps are presented and discussed in each section.

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Photocatalytic C(sp3) radical generation via C–H, C–C, and C–X bond cleavage

An efficient Ru doped hydrotalcite catalyzed N-alkylation of benzamides and sulfonamides with alcohols via borrowing hydrogen catalysis is illustrated. Various primary alcohols, including benzyl, heteroaryl, and aliphatic alcohols, were alkylated in good to excellent yields. To shed light on the mechanistic details, several control studies and deuterium labeling experiments were performed. Mechanistic studies underpin that the reaction is going via a borrowing hydrogen pathway rather than an SN1 type mechanism. The reaction can be easily scaled up without any detrimental effect on the yield. The catalyst is also capable of synthesizing quinazolinone directly from 2-aminobenzamide and alcohols. Successful recyclability and high reactivity highlight the practical applicability of the catalyst.

Ru Doped Hydrotalcite Catalyzed Borrowing Hydrogen-Mediated N-Alkylation of Benzamides, Sulfonamides, and Dehydrogenative Synthesis of Quinazolinones.

PIDA-mediated oxidative aromatic CN bond cleavage: Efficient methodology for the synthesis of 1,2-diaza-1,3-dienes under ambient conditions

Herein, we disclose a protocol to synthesize trisubstituted alkenyl thioethers through a direct S-alkylation of 1,2,3-thiadiazoles with C-radical precursors, 4-alkyl-1,4-dihydropyridines (DHPs), driven by visible-light photocatalysis. A broad range of primary, secondary, and tertiary C-radical precursors, DHPs, are suitable for this reaction and the desired products can be obtained in good to excellent yields under mild conditions. Remarkably, high stereoselectivity with Z-alkenyl thioethers was achieved in the presence of a Cu(OAc)2 catalyst. Synergistic experimental and computational studies were carried out to shed light on the mechanisms of this reaction, in which the quenching pathway of an excited photocatalyst (*RuII) could be altered in the presence of the Cu(OAc)2 catalyst. A reductive quenching pathway (RuII/*RuII/RuI/RuII) is proposed in the absence of the Cu(OAc)2 catalyst while an oxidative quenching pathway (RuII/*RuII/RuIII/RuII) is suggested with the assistance of the Cu(OAc)2 catalyst. In addition, the origin of the Z-selectivity of the product is discussed.

Visible-light photocatalytic preparation of alkenyl thioethers from 1,2,3-thiadiazoles and Hantzsch esters: synthetic and mechanistic investigations

The construction of C(sp3)–N bonds via direct radical–radical cross-coupling under benign conditions is a desirable but challenging approach. Herein, the cross-coupling of alkyl and amidyl radicals...

Nickel/Photoredox Dual Catalytic Cross-Coupling of Alkyl and Amidyl Radicals to Construct C(sp3)–N Bonds

Oxidative Ring-Opening of 1H-Pyrazol-5-amines and Its Application in Constructing Pyrazolo–Pyrrolo–Pyrazine Scaffolds by Domino Cyclization

Understanding Mechanistic Differences between 3-Diazoindolin-2-Imines and N-Sulfonyl-1,2,3-Triazoles in the Rh2(II)-Catalyzed Reactions with Nitrosoarenes

Shaofang Zhou

Papers

Nickel/Photoredox Dual Catalytic Cross-Coupling of Alkyl and Amidyl Radicals to Construct C(sp3)–N Bonds

Oxidative Ring-Opening of 1H-Pyrazol-5-amines and Its Application in Constructing Pyrazolo–Pyrrolo–Pyrazine Scaffolds by Domino Cyclization

Visible-light photocatalytic preparation of alkenyl thioethers from 1,2,3-thiadiazoles and Hantzsch esters: synthetic and mechanistic investigations

Understanding Mechanistic Differences between 3-Diazoindolin-2-Imines and N-Sulfonyl-1,2,3-Triazoles in the Rh2(II)-Catalyzed Reactions with Nitrosoarenes