The use of carboxylic acids as convenient and easily accessible cross-coupling handles can be grouped into two categories: those that leverage the free carboxylic acid and those that use a redox-active ester (RAE) capable of SET derived from the corresponding carboxylic acid. Amongst these two sets of starting materials, there are three distinct catalytic cycles that are operative depending on one's choice of starting material and means of activation. These include (i) cross-coupling of RAEs with nucleophiles, (ii) cross-coupling of RAEs with electrophiles and (iii) oxidative activation of free acids (Figure ). Aside from approaches that involve transition metal catalyzed process (programmed coupling) , tactics that rely on the innate reactivity of an unfunctionalized heterocycle to radical addition have been well explored in the context of the Minisci reaction. While such reports employ carboxylic acid starting materials, they are outside the scope of this perspective and have been reviewed elsewhere. Within the first category, it has been shown that NHPI and TCNHPI RAEs can engage in cross-coupling with a variety of C(sp 2 ) aryl organozinc coupling partners under Ni-catalysis. Since then, the scope of this transformation has been expanded to a broad range of aryl, 20 alkenyl 21 and alkynyl organometallic reagents including organoboron species as well as Grignard reagents under Fe-catalysis. Mechanistically, these couplings are hypothesized to proceed by initial transmetallation of the C(sp 2 ) nucleophile equivalent to a Ni(I) species. The corresponding Ni(I) complex then donates an electron to the RAE generated a cationic Ni(II) intermediate. Upon reduction by the Ni(I), the RAE fragments to liberate CO2 and phthalimide to generate a carbon-centered radical. This radical then rapidly recombines with the Ni(II) to afford a Ni(III) intermediate that upon reductive elimination generates the cross coupled product and a Ni(I) species that can re-enter the catalytic cycle. Operationally these reactions are akin to amide-bond formation wherein the RAE can be prepared in situ and used directly upon exposure to the organometallic nucleophile and catalyst.