Herein, we report a methodology to access isotopically labeled esters and amides from carbonates and carbamates employing an oxygen deletion strategy. This methodology utilizes a decarboxylative carbonylation approach for isotope labeling with near stoichiometric, ex situ generated 12C, or 13C carbon monoxide. This reaction is characterized by its broad scope, functional group tolerance, and high yields, which is showcased with the synthesis of structurally complex molecules. A complementary method that operates by the catalytic in situ generation of CO via the reduction of CO2 liberated during decarboxylation has also been developed as a proof-of-concept approach that CO2-derived compounds can be converted to CO-containing frameworks. Mechanistic studies provide insight into the catalytic steps which highlight the impact of ligand choice to overcome challenges associated with low-pressure carbonylation methodologies, along with rational for the development of future methodologies.