Visible light/copper catalysis enabled alkylation of silyl enol ethers with arylsulfonium salts

Ultrasound-Assisted Remote Benzylic C(sp3)-H Alkylation of N-Fluoroamides with Enol Silanes

We have developed an ultrasound-assisted remote benzylic C(sp3)-H alkylation of N-fluorobenzamides with enol silanes; a series of β-aryl substituted propiophenones was generated in good to high yields. This reaction represents a formal C(sp3)-C(sp3) coupling and features simplicity, high efficiency, and wide substrate scope in a multiple-step sequential process, which involves N-F homolysis, 1,5-hydrogen atom transfer, benzylic radical addition, oxidation by copper(II) salt, and removal of the trimethylsilyl group. Also, DFT theoretical calculations and Marcus theory were employed to consolidate the proposed reaction mechanism.

Non-directed oxidative annulation of 2-arylindazoles with electron deficient olefins via visible light photocatalysis

A new visible-light-mediated non-directed oxidative annulation between 2-arylindazoles and electron-deficient olefins using commercially available piperidine-1-sulfonyl chloride as the radical precursor to afford fused 5,6-dihydroindazolo[2,3-a]quinolines has been developed under mild reaction conditions. This transformation occurs via two consecutive C-H bond functionalizations. The mechanistic investigation results indicate that the reaction progresses through a radical pathway forming a 2-(2-aryl-2H-indazol-3-yl)-3-piperidin-1-ylsulfonyl derivative as an intermediate.

Harnessing Bromo/Acyloxy Transposition (BrAcT) and Excited-State Copper Catalysis for Styrene Difunctionalization

1,2-Difunctionalization of styrenes, adding two distinct functional groups across the C═C double bond, has emerged as a powerful tool for enhancing molecular complexity. Herein, we report the development of a regioconvergent β-acyloxylation-α-ketonylation of styrenes through bromo/acyloxy transposition (BrAcT) and excited-state copper catalysis. This approach is amenable to gram-scale synthesis and tolerates a wide range of functional groups and complex molecular frameworks, including derivatives of natural products and marketed drugs. Our experimental and computational studies suggest a unique mechanism featuring a dynamic, ionic BrAcT process and excited-state copper-catalyzed redox reactions. We anticipate that this BrAcT process could serve as a broadly applicable and versatile strategy for β-acyloxylation-α-functionalization of styrenes, creating valuable intermediates for preparing new pharmaceuticals, agrochemicals, and functional materials.

Photoredox Ring Opening 1,2-Alkylarylation of Alkenes with Sulfonium Salts Toward Thioether-Substituted Oxindoles

A novel strategy for the difunctionalization of electron-deficient alkenes with aryl sulfonium salts to access remote sulfur-containing oxindole derivatives by using in situ-formed copper(I)-based complexes as a photoredox catalyst is presented. This method enables the generation of the C(sp3)-centered radicals through site selective cleavage of the C-S bond of aryl sulfonium salts under mild conditions. Moreover, the oxidation reactions of desired products provide a new strategy for the preparation of sulfoxide or sulfone-containing compounds. Importantly, this approach can be easily applied to late-stage modification of pharmaceuticals molecules.

Silylation of 2H-indazoles by photoinduced hydrogen atom transfer catalysis

A metal-free, visible-light-mediated C-H silylation of 2H-indazoles with triphenylsilane has been developed employing 4CzIPN as a photocatalyst and triisopropylsilanethiol as a hydrogen atom transfer (HAT) reagent under aerobic reaction conditions. This method shows tolerance toward many functional groups and affords a variety of silylated indazoles at up to 89% yield. The experimental results suggest that the reaction progresses through a radical pathway.