Driven by the inherent synthetic potential of CO as an abundant, inexpensive and renewable C chemical feedstock, the recent years have witnessed renewed interest in devising catalytic CO fixations into organic matter. Although the formation of C-C bonds via catalytic CO fixation remained rather limited for a long period of time, a close look into the recent literature data indicates that catalytic carboxylation reactions have entered a new era of exponential growth, evolving into a mature discipline that allows for streamlining the synthesis of carboxylic acids, building blocks of utmost relevance in industrial endeavors. These strategies have generally proven broadly applicability and convenient to perform. However, substantial challenges still need to be addressed reinforcing the need to cover metal-catalyzed carboxylation area in a conceptual and concise manner, delineating the underlying new principles that are slowly emerging in this vibrant area of expertise.

An integrated catalytic decarboxylation/carboxylation for accessing isotopically labeled carboxylic acids with 13CO2 or 14CO2 is described. The method shows a wide scope under mild conditions, even in the context of late-stage functionalization, and does not require stoichiometric organometallics, thus complementing existing carbon-labeling techniques en route to carboxylic acids.

A site-selective catalytic incorporation of multiple CO molecules into 1,3-dienes en route to adipic acids is described. This protocol is characterized by its mild conditions, excellent chemo- and regioselectivity and ease of execution under CO (1 atm), including the use of bulk butadiene and/or isoprene feedstocks.

A switchable site-selective catalytic carboxylation of allylic alcohols has been developed in which CO is used with dual roles, both facilitating C-OH cleavage and as a C source. This protocol is characterized by its mild reaction conditions, absence of stoichiometric amounts of organometallic reagents, broad scope, and exquisite regiodivergency which can be modulated by the type of ligand employed.