The activation and conversion of carbon dioxide into organic products have attracted researchers over the years despite the high thermodynamic stability and kinetic inertness of this molecule. With the rise of new synthetic strategies for the CO₂ activation, comes the need for mechanistic studies which can help the rationalization of the outcomes and thus enable improvements in the design of future reaction schemes. In this regard, computational chemistry has proven over time to be a powerful tool. In particular the computation of reaction pathways using Density Functional Theory (DFT) methods is an established method for mechanistic elucidation of regio- and stereoselective reactions.

In this thesis we set out to study the reaction mechanism for a number of transition metal-catalyzed reactions related to the activation of carbon dioxide. We chose a few landmark carboxylation reactions and also the conversion of cyclic carbonates, which are one of the important initial products from CO₂ activation. We applied DFT methods combined with tools such as microkinetic modeling to clarify the mechanisms.

For the carboxylation reactions, we selected to study the mechanism of palladium-catalyzed allene carboxylation reaction and the conversion of siloxy silane to hydroxy acids. For the conversion of  cyclic vinyl carbonates, we studied two reactions involving a decarboxylative approach catalyzed by palladium complexes. we analyzed the conversion of cyclic vinyl carbonates to allylic amines by using aniline as the nucleophile and we studied the behavior of the same catalytic system in the absence of the nucleophilic amine.