Hantzsch Ester as a Visible‐Light Photoredox Catalyst for Transition‐Metal‐Free Coupling of Arylhalides and Arylsulfinates

Abstract

Diethyl 2,6‐dimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate (HEH) has been utilized as a visible‐light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE−, single electron transfer (SET) in donor–acceptor complex (DAC) from *HE− to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE. to sulfone by the DAC method.

Expedient Dual Co/Organophotoredox Catalyzed Stereoselective Synthesis of All‐Carbon Quaternary Centers

“…In the absence of PC, the reaction showed a slight background reactivity (22 % yield), which we assigned to minimal light absorption and subsequent light-induced electron transfer by the HE. [13] It is worth noting that coupling on the less-hindered allylic carbon center to produce linear regioisomeric products was not observed, in contrast to earlier reports. [8a, 10a] The optimized conditions were then applied to a larger set of reaction partners, and first the scope of aldehydes was examined (Scheme 2).…”

Visible-light mediated cross-coupling of aryl halides with sodium sulfinatesviacarbonyl-photoredox/nickel dual catalysis

“…A subsequent Pd-catalyzed amination with piperazine would afford 3-( phenylsulfonyl)-8-( piperazin1-yl)quinoline as a potential Alzheimer's disease chemotherapeutic molecule. 24 Sulfonylation of benodanil under the optimal reaction conditions gave the sulfonylated product N-phenyl-2-( phenylsulfonyl)benzamide in 83% isolated yield. The cross coupling reaction of the product 3ab with carbazole in the presence of K 2 CO 3 in DMF at 100 °C afforded 4-((4-(9H-carbazol-9-yl) phenyl)sulfonyl)benzonitrile in 91% yield.…”

Visible Light as the Key for the Formation of Carbon–Sulfur Bonds in Sulfones, Thioethers, and Sulfonamides: An Update

“…Without the need for sacrificial agents or other mediators, aryl sulfones can be easily obtained (Scheme 12). 19 The mechanism relies on the peculiar capacity of the Hantzsch ester (HE) to activate halides generating an electron donor-acceptor (EDA) complex (Scheme 12). Indeed, upon deprotonation, the HEanionic species can interact with the halide 18 to produce the EDA complex [ In 2019, Yadav proposed another cross-coupling strategy starting from 1.…”