The utilization of CO2 is receiving significant attention not only as a means to mitigate CO2 emissions but also to employ it as a sustainable C1 source for producing chemicals and fuels. Among various approaches, ethylene carboxylation using CO2 has emerged as a promising method for acrylate synthesis. Although late transition metals such as Ni and Pd have been extensively studied for catalytic acrylate synthesis since the 2010s, these catalytic systems still exhibit limited activity and require harsh reaction conditions. Therefore, the exploration of alternative catalytic systems is essential for developing more effective carboxylation reactions.
Here, we investigated acrylate synthesis using a titanium complex as a potential alternative to conventional late transition metal catalysts. The elementary steps toward acrylate synthesis were explored using titanocene complexes. The formation of a titanalactone complex from CO2 and ethylene was revisited to elucidate the kinetic and thermodynamic advantages offered by an early transition metal in metallalactone formation. The subsequent conversion of titanalactone to acrylate was evaluated through various reaction pathways. Although the strong titanium-oxygen bond inhibits β-hydride elimination, an alternative pathway employing strong bases and additives resulted in direct deprotonation to produce acrylate in high yield. This study provides fundamental insights into the opportunities and challenges associated with catalytic acrylate synthesis utilizing an early transition metal.