Decarboxylative\nCross-Coupling Enabled by Fe and Ni\nMetallaphotoredox Catalysis

Decarboxylative cross-coupling\nof carboxylic acids and aryl halides\nhas become a key transformation in organic synthesis to form C(sp<sup>2</sup>)–C(sp<sup>3</sup>) bonds. In this report, a base metal\npairing between Fe and Ni has been developed with complementary reactivity\nto the well-established Ir and Ni metallaphotoredox reactions. Utilizing\nan inexpensive FeCl<sub>3</sub> cocatalyst along with a pyridine carboxamidine\nNi catalyst, a range of aryl iodides can be preferentially coupled\nto carboxylic acids over boronic acid esters, triflates, chlorides,\nand even bromides in high yields. Additionally, carboxylic acid derivatives\ncontaining heterocycles, <i>N</i>-protected amino acids,\nand protic functionality can be coupled in 23–96% yield with\na range of sterically hindered, electron-rich, and electron-deficient\naryl iodides. Preliminary catalytic and stoichiometric reactions support\na mechanism in which Fe is responsible for the activation of carboxylic\nacid upon irradiation with light and a Ni<sup>I</sup> alkyl intermediate\nis responsible for activation of the aryl iodide coupling partner\nfollowed by reductive elimination to generate product.