Yuan Cai

The simultaneous construction of C-C and C-X bonds in a single step facilitates multistep synthesis through rapid carbon chain growth and subsequent transformations of halide functionalities. Traditional Kharasch addition requires simple polyhalogenated compounds or those with electron-withdrawing groups at the α-carbon. Herein, we present a Kharasch-type reaction utilizing a broad range of carboxylic acid-derived redox-active esters as the alkyl source, which enables the efficient introduction of highly functionalized alkyl groups. Our method produces α-halo carbonyls that enable versatile nucleophilic substitutions for synthesizing valuable compounds, such as unnatural α-amino acids.

Sigma bond cleavage through electronically excited states allows synthetically useful transformations with two radical species. Direct excitation of simple aryl halides to form both aryl and halogen radicals necessitates UV-C light, so undesired side reactions are often observed and specific equipment is required. Moreover, only aryl halides with extended π systems and comparatively low triplet energy are applicable to synthetically useful energy transfer catalysis. Here we show the conceptual advantages of arylthianthrenium salts (ArTTs) for energy transfer catalysis with high energy efficiency compared to conventional aryl (pseudo)halides and their utility in arylation reactions of ethylene. The fundamental advance is enabled by the low triplet energy of ArTTs that may originate in large part from the electronic interplay between the distinct sulfur atoms in the tricyclic thianthrene scaffold, which is not accessible in either simple (pseudo)halides or other conventional sulfonium salts.

Sigma bond cleavage through electronically excited states allows synthetically useful transformations with two radical species. Direct excitation of simple aryl halides to form both aryl and halogen radicals necessitates UV-C light, so undesired side reactions are often observed, and specific equipment is required. Moreover, only aryl halides with extended pi systems and comparatively low triplet energy are applicable to synthetically useful energy transfer catalysis with visible light. Here we show the conceptual advantages of arylthianthrenium salts (ArTTs) for energy transfer catalysis with visible light in high quantum yield as compared to conventional aryl(pseudo)halides, and their utility in arylation reactions of ethylene. The fundamental advance is enabled by the low triplet energy of ArTTs that may originate in large part from the electronic interplay between the distinct sulfur atoms in the tricyclic thianthrene scaffold, which is neither accessible in simple (pseudo)halides nor other conventional sulfonium salts.

A visible‐light‐induced, three‐component palladium‐catalyzed 1,4‐aminoarylation of butadienes with readily available aryl halides and aliphatic amines has been developed, affording allylamines with excellent E‐selectivity. The reaction exhibits exceptional control over chemo‐, regio‐, and stereoselectivity, a broad substrate scope, and high functional group compatibility, as demonstrated by the late‐stage functionalization of bioactive molecules. Mechanistic investigations are consistent with a photoinduced radical Pd(0)‐Pd(I)‐Pd(II)‐Pd(0) Heck‐Tsuji–Trost allylation cascade.

A visible‐light‐induced, three‐component palladium‐catalyzed 1,4‐aminoarylation of butadienes with readily available aryl halides and aliphatic amines has been developed, affording allylamines with excellent E‐selectivity. The reaction exhibits exceptional control over chemo‐, regio‐, and stereoselectivity, a broad substrate scope, and high functional group compatibility, as demonstrated by the late‐stage functionalization of bioactive molecules. Mechanistic investigations are consistent with a photoinduced radical Pd(0)‐Pd(I)‐Pd(II)‐Pd(0) Heck‐Tsuji–Trost allylation cascade.

Photoelectrochemical (PEC) seawater splitting is a promising method for the direct utilization of solar energy and abundant seawater resources for hydrogen production. Photoelectrodes are susceptible to various ions in seawater and complicated competitive reactions, resulting in the failure of photoelectrodes. This paper proposes the design and fabrication of different sputtered stainless steel (SS) films deposited on silicon photoanodes, completely isolating the electrolytes and semiconductor substrate. Upon coupling with the PEC flow cell, the back-illuminated photoanode coated with 316 SS cocatalyst achieves stable operation for 70 h in natural seawater with a highly alkaline KOH (30 wt.%, 7.64 mol/L) electrolyte due to the remarkable protection effect of the substrate from stainless steel, while the PEC seawater splitting system achieves a record hydrogen production rate of 600 μmol/(h·cm²). An appropriate Ni/Fe ratio in the SS ensures remarkable oxygen evolution activity, while chromic oxide ensures the effective anticorrosion effect by adjusting the microenvironment of the photoanodes. Moreover, fabricating PEC flow cells with photoanodes coated with SS cocatalysts are a viable strategy for PEC seawater splitting.

The arylethylamine pharmacophore is conserved across a range of biologically active natural products and pharmaceuticals, particularly in molecules that act on the central nervous system. Herein, we present a photoinduced copper-catalyzed azidoarylation of alkenes at a late stage with arylthianthrenium salts, allowing access to highly functionalized acyclic (hetero)arylethylamine scaffolds that are otherwise difficult to access. A mechanistic study is consistent with a rac-BINAP-Cu^I-azide (2) as the photoactive catalytic species. We show the utility of the new method by the expedient synthesis of racemic melphalan in four steps through C-H functionalization.