Nickel-Catalyzed LiCl-Controlled Switchable Carboxylation of Aryl C-F Bonds with One or Two Molecules of CO2

The use of CO2 as a renewable C1 source for the synthesis of value-added chemicals can contribute to a more sustainable chemistry. In this work, a nickel-catalyzed amide-directed carboxylation of aryl C-F bonds with CO2 has been developed. The reaction is switchable controlled by LiCl to react with one or two molecules of CO2 to afford valuable phthalimides or alpha-hydroxycarboxylic acid derivatives. Further study shows that the reaction is a step-by-step process. The first step is a nickel-catalyzed carboxylation of aryl C-F bonds with CO2 and tandem cyclization to afford phthalimides. The second step is a nickel-catalyzed C-N bond carboxylation of phthalimides with CO2, and intramolecular nucleophilic addition of amide anion to the carbonyl. The carboxylation of phthalimides with CO2 is also developed based on this reaction. The work features inert C-F bond functionalization, amide C-N bond activation, and multiple CO2 incorporation. Mechanistic studies indicate that the azanickelacycle intermediates play an important role, and LiCl facilitates the reduction of Ni(II) to Ni(I) and promotes the carboxylation with the second molecule of CO2. This protocol provides an efficient route for C-F bond functionalization under mild conditions via the chemical fixation of one or two molecules of CO2.