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Visible-Light/Nickel-Catalyzed Carboxylation of C(sp2) Bromides via Formate Activation

Gavin C. Smith, Drason H. Zhang, Wanli Zhang, Abigail H. Soliven and William M. Wuest*

*Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States, Email:

G. C. Smith, D. H. Zhang, W. Zhang, A. H. Soliven, W. M. Wuest, J. Org. Chem., 2023, 88, 9565-9568.

DOI: 10.1021/acs.joc.3c00895

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Visible light mediates a carboxylation of (hetero)aryl/vinyl bromides using catalytic 4CzIPN, nickel, phenyl triflimide, and sodium formate as a carboxylation agent. Phenyl triflimide plays an essential role in promoting the reaction. The reaction avoids the use of harsh reagents or gaseous carbon dioxide and enables a mild and facile construction of carboxylic acids from readily available starting materials.

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General Photoredox Reaction Setup

To run multiple reactions, an appropriately sized 3D printed carousel was used, which exposed the reactions to the blue light evenly (photo 1). While our 3D printed carousel was helpful for screening reactions, it is not necessary in this system - any rack will suffice and our scaled reactions are simply held by a clampl. A 15 W LED array lamp was used as a blue light source (photo 2,3). These lamps were routinely used for up to 12 reactions at a time (photo 2,3). The blue LEDs were positioned approximately 6 inches above the reaction vials to get good light coverage without overheating the reactions (photo 2,3).

General Procedure

A 20 mL screw-top test tube was charged with 4CzIPN (1 mol%), sodium formate (1.5 equiv), N-phenyl-bis(trifluoromethanesulfonimide) (15 mol%) and [4,4-Bis(1,1-dimethyl)-2,2-bipyridine] nickel (II) bromide (10 mol%)) and substrate (1 equiv., if solid). The tube was equipped with a stir bar and was sealed with a PTFE/silicon septum. The atmosphere was exchanged by applying vacuum and backfilling with argon (this process was conducted a total of three times). Under argon atmosphere, separately the indicated degassed solvent (0.1 M) was added via syringe followed by the substrate (if liquid, 1.0 equiv). The resulting mixture was stirred at 1400 RPM for 16 h under irradiation by blue LEDs. 1M HCl was added and then the reaction mixture was extracted with ethyl acetate (3 x). The organic layer was dried over MgSO4 and concentrated. The residue was purified on silica using the indicated solvent mixture as eluent to afford the title compound.

Key Words

carboxylation, photochemistry

ID: J42-Y2023