The recent years
have witnessed the development of metal-catalyzed
reductive carboxylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing
methodologies for preparing carboxylic acids, privileged motifs in
a myriad of pharmaceuticals and molecules displaying significant biological
properties. While originally visualized as exotic cross-coupling reactions,
a close look into the literature data indicates that these processes
have become a fertile ground, allowing for the utilization of a variety
of coupling partners, even with particularly challenging substrate
combinations. As for other related cross-electrophile scenarios, the
vast majority of reductive carboxylation of organic (pseudo)halides
are characterized by their simplicity, mild conditions, and a broad
functional group compatibility, suggesting that these processes could
be implemented in late-stage diversification. This perspective describes
the evolution of metal-catalyzed reductive carboxylation of organic
(pseudo)halides from its inception in the pioneering stoichiometric
work of Osakada to the present. Specific emphasis is devoted to the
reactivity of these coupling processes, with substrates ranging from
aryl-, vinyl-, benzyl- to unactivated alkyl (pseudo)halides. Despite
the impressive advances realized, a comprehensive study detailing
the mechanistic intricacies of these processes is still lacking. Some
recent empirical evidence reveal an intriguing dichotomy exerted by
the substitution pattern on the ligands utilized; still, however,
some elementary steps within the catalytic cycle of these reactions
remain speculative, in many instances invoking a canonical cross-coupling
process. Although tentative, we anticipate that these processes might
fall into more than one distinct mechanistic category depending on
the substrate utilized, suggesting that investigations aimed at unraveling
the mechanistic underpinnings of these processes will likely bring
new and innovative research grounds in this vibrant area of expertise.