Decarboxylative Cross-Coupling Enabled by Fe and Ni Metallaphotoredox Catalysis

Decarboxylative cross-coupling of carboxylic acids and aryl halides has become a key transformation in organic synthe- sis to form C(sp2)–C(sp3) bonds. In this report, a base metal pairing between Fe and Ni has been developed with complementary reactivity to the well-established Ir and Ni metallaphotoredox reactions. Utilizing an inexpensive FeCl3 co-catalyst along with a pyr- idine carboxamidine Ni catalyst, a range of aryl iodides can be preferentially coupled to carboxylic acids over boronic acid esters, triflates, chlorides, and even bromides in high yields. Additionally, carboxylic acid derivatives containing heterocycles, N-protected amino acids, electron-rich amines, and protic functionality can be coupled in 23-96% yield with a range of sterically hindered, elec- tron-rich, and electron-deficient aryl iodides. Preliminary catalytic and stoichiometric reactions support a mechanism in which Fe is responsible for the activation of carboxylic acid upon irradiation with light and a Ni(I)alkyl intermediate is responsible for activation of the aryl iodide coupling partner followed by reductive elimination to generate product.