Carbon dioxide (CO₂) is present in our atmosphere as the fourth most abundant gas. The non-toxicity and non-flammability of CO₂ makes it an attractive C1-synthon in organic synthesis. This thesis aims to develop catalytic transformations to utilize CO₂ in the preparation of organic compounds, namely carboxylic acids and cyclic carbonates. The developed methods center around photoredox chemistry, electrochemistry, homogeneous catalysis, and heterogeneous catalysis. Synthesis of carbon-isotope-labeled organic compounds from isotopic CO₂ which are of great importance in medicinal chemistry was also presented.

Due to the inertness of CO₂, activation of either CO₂ or other starting materials by photocatalysis or electrocatalysis facilitates the incorporation of CO₂ into organic compounds. By using a photoredox catalyst under visible light irradiation, highly reactive carbanions can be formed from common feedstocks, such as sulfinate salts and alkenes. The electron-dense carbanions readily react with ¹³CO₂ to yield ¹³C-labeled aliphatic carboxylic acids. On the contrary, CO₂ can be electrochemically reduced to the more reactive CO, which can readily undergo palladium-catalyzed hydroxycarbonylation with aryl iodides to yield benzoic acids. In this work, tandem reactions based on the use of recyclable heterogeneous catalysis have been developed for this transformation.

Epoxides are ring-strained molecules that can undergo cycloaddition reactions with CO₂ to yield cyclic carbonates. In this thesis, a stereospecific catalytic approach for accessing ¹³C- and ¹⁴C-labeled chiral cyclic carbonates using near stoichiometric amount of CO₂ was developed. The labeled chiral cyclic carbonates serve as precursors for the synthesis of isotope-labeled pharmaceuticals. Furthermore, an auto-relay heterogeneous catalysis approach was developed to obtain epoxides from readily available alkenes in a chemoselective manner, which can further react with CO₂ to form cyclic carbonates.